Guidance

Seizures of drugs in England and Wales: user guide

Updated 18 January 2024

Applies to England and Wales

1. Introduction

This user guide is intended as a useful reference with explanatory notes on the issues and classifications key to the production and presentation of the Home Office’s annual release Seizures of drugs in England and Wales statistics. Analysts in the Drugs Research Team, which is part of the Drugs Exploitation and Abuse Analysis Unit, prepare the annual release and accompanying datasets. The Home Office is consulting with stakeholders on this year’s publication with a survey that can be access here. The survey closes on 1st May 2024.

1.1 Statistics covered

The statistics in Seizures of drugs in England and Wales relate to the seizures of drugs controlled under The Misuse of Drugs Act (MDA) 1971, which came into force on 1 July 1973, and The Psychoactive Substances Act (PSA) 2016, which came into force on 26 May 2016. They cover seizures made during the year by police forces in England and Wales (including the British Transport Police) and Border Force. Border Force used to be part of the UK Border Agency (UKBA). Although Border Force will have made seizures outside the land territory of England and Wales (for example, Scotland and Northern Ireland), such seizures are excluded from figures presented in the publication.

The release draws together statistics on the following topics:

• number of seizures
• quantity of drugs seized
• seizures by authority (meaning comparisons between police forces and Border Force)

Seizures of drugs statistics are presented on a financial year (FY) basis (1 April to 31 March).

Seizures involving more than one drug are counted as a single seizure in the total number of seizures. However, seizures are also counted separately against each individual drug type and drug class involved. For example, a seizure of powder cocaine and herbal cannabis would be recorded as one overall seizure, one Class A, one Class B, one powder cocaine, one herbal cannabis and one total cannabis seizure (see Chapter 3). Annual movements in quantities are often heavily affected by a few very large seizures.

Further details on coverage in this release and classification of drugs under the MDA are in Chapter 3.

The Home Office first collated drug seizure statistics in an electronic format in 1974, originally covering the United Kingdom rather than England and Wales. Since the MDA was introduced, there have been various changes to which drugs are covered by the Act and to recording practices by police forces and other agencies. As such, drug seizure statistics are not directly comparable from year to year. Nor are they a measure of drug prevalence in society.

In the financial year ending 31 March 2018, information on seizures of new psychoactive substances (NPS) was recorded systematically across police forces and Border Force for the first time. NPS refers to newly available drugs that mimic the effect of existing drugs such as cannabis, ecstasy, and powder cocaine. Some NPS are controlled under the MDA, while other NPS are illegal to supply, produce and import under the Psychoactive Substances Act 2016. Data on NPS seizures is included in publications for years ending March 2018 to 2023 in the Appendix tables, and designated as experimental statistics, as they are not fully developed and do not meet the rigorous quality standards of Official Statistics.

Gamma-Hydroxybutyric Acid (GHB), and the closely-related substances Gamma-Butyrolactone (GBL) and 1,4-Butanediol (1,4-BD) were reclassified from Class C to Class B on 13 April 2022. Police force seizures of GHB are reported as a Class B drug across all years of the publication, and GBL and 1,4-BD will be reported under ‘Other Class B’. Border Forces seizures of GHB, GBL and 1,4-BD will be reported as Class B drugs from 2020/21 onwards. However due to limitations with Border Force data, seizures of GHB, GBL and 1,4-BD made prior to year ending March 2021 will be reported as ‘Other Class C’ drugs.

1.2 Quality and methodology

The data used in this release has been collected by police forces and forms part of the statutory Annual Data Requirement between the Home Office and police forces (including Border Force).

The published figures on drug seizures are sourced from police forces’ operational records. Although care is taken in completing and analysing the returns used to compile the figures in this release, the figures are subject to the inaccuracies of any large-scale recording system of this kind that involves different organisations. The Home Office is continually working with police forces to understand fully the processes and limitations of the data, as well as working to improve it.

The section below considers the process before the data is submitted to the Home Office. It outlines the key characteristics and limitations of the statistics. Where there are limitations, the implications of these in terms of uses of the data are outlined. The strengths and limitations of the data vary from force to force depending on specific internal data collection and quality assurance procedures.

At the start of the data collection process, the Home Office sends a Microsoft Excel template to every police force to compile their drug seizure statistics. This template has comprehensive checks built into it to ensure any incorrect values are picked up at this data collection stage. The template also ensures that each drug is correctly classified, and that the preparation type (for example, kilograms or doses) entered by the force is valid for the specified drug. Though this process highlights any initial quality concerns, there are other limitations to the data (table 1).

Table 1: Limitations and implications of drug seizures data

Limitations	Implications
Data relies on police forces correctly recording and entering drug seizures on their systems	Although any obvious errors would be highlighted in the quality assurance checks conducted by both the data suppliers and the data producers, it is possible that some data may not be totally accurate. This is likely to be the case with any large-scale recording system that involves several different organisations. More details are provided below on how Home Office analysts work with police forces to ensure data quality
Not all drugs seized by police forces are tested by forensics. For drugs that are not tested by forensics, accuracy of the data relies on the officer correctly identifying the substance, or the offender stating what the substance is	There is a small chance that some drugs have not been identified (and therefore classified) correctly. This will not affect the total number of drugs seized but could affect the more detailed statistics. It is unlikely that the main drugs reported on in the publication would be misclassified (for example, cannabis, powder cocaine, ecstasy)
Forces can seize drugs in different preparation types (last updated in 2005). The Home Office uses conversion factors to convert the quantity of seizures into 1 comparable unit	Most conversion factors have not been updated since 20051, therefore it is possible that some quantity data (especially for those drugs where quantity is reported in terms of doses) is not entirely accurate. However, the same conversion factors have been used throughout the time series so the data on trends can be considered consistent
Changes in force systems meaning only a partial return can be submitted to the Home Office	Several forces have changed their data recording systems in the past few years, which has resulted in the loss of some drug seizures data and therefore a partial return from that year. An estimation technique is used to estimate for missing or inaccurate data
During the quality checks for the year ending March 2015 publication, it became apparent that police forces had different ways of recording seizures of large amounts of cannabis plants from 1 cannabis farm. To ensure consistency in recording practices, forces received guidance explaining that if it is not possible to count every cannabis plant seized, then an estimate should be made instead	The number of cannabis plants seized by police forces may be estimates in some cases. This does not affect the total number of seizures but will impact the quantity of plants seized

Notes:

1. With the exception of nitrous oxide. A new conversion factor was agreed in 2023 for nitrous oxide, to allow all preparations of nitrous oxide to be reported in the publication. Prior to this, nitrous oxide recorded in litres and kg were excluded from publication.

1.2.1 Quality assurance by the Home Office

All the data received by the Home Office undergoes a strict quality assurance process to ensure it is fit for purpose and published to the highest standard. Any data quality issues are flagged and subsequently reconciled with forces. Before publication, data is combined into tables and sent back to forces to be signed off prior to publication to ensure it is accurate. Details of any known data quality issues are included in the relevant part of the bulletin, and/or data tables.

While all data undergoes a thorough quality assurance process, the level of accuracy varies according to factors such as, the type of drug seized, the likelihood of error in the data provided by forces, and what the data is used for. Data that is widely used will undergo the highest level of quality assurance. Other data will undergo a more limited but proportionate level. The quality assurance checks include looking for:

• missing and/or incomplete data
• inconsistencies in the data
• extreme values
• invalid quantities
• known issues, as mentioned in table 1

Once these checks have been completed, Home Office analysts undertake trend analysis to look for unusual or unexpected trends in the data. Any inconsistencies or unusual trends are flagged to forces. They are then asked to explain the trends or submit amended data.

Where an error is spotted, Home Office analysts consider whether this is likely to be a force-specific issue, or whether other forces should be notified to ensure consistency of data between forces. Recent examples of errors and or issues spotted, and the action subsequently taken, include:

Incorrect quantity of drugs recorded for LSD: in some cases, LSD is recorded against the ‘weighed’ preparation type which, after applying conversion factors, would be converted to tens of thousands of doses. Checks of LSD seizures are conducted by Home Office analysts and queried with forces. Where errors are found, revised data is submitted.

Recording of number of cannabis plants per seizure: sometimes the number of cannabis plants seized per seizure is recorded as ‘1’. In the past ‘1’ was recorded by default when there were too many plants to count. Home Office analysts have worked with police forces to ensure these seizures are more accurately recorded and the number of single cannabis plant seizures is now embedded in the data quality checks.

1.3 Imputation of data

In some years, certain forces could not supply the Home Office with accurate or complete drug seizures data. This may be due to several reasons, including:

• the police force has changed processes around the recording of drug seizures which have taken time to bed in
• changes in police force IT systems
• identification of errors by either the police force or Home Office analysts

Where a police force could not send data deemed suitable for publication, the Home Office has imputed seizure and quantity values for that force, that is, using alternative values in place of missing data. This is done with the agreement of the police force, and only when the Home Office and force agree that imputation of data is likely to give a more accurate figure for their police force than using the data they hold. The imputation methods used in year ending 31 March 2023 and in previous years are in table 2.

Table 2: Imputation methods used for missing or incomplete data from police forces

Year ending March	Police force	Data supplied	Imputation method
2013	Hampshire Constabulary	None	Number and quantity of seizures estimated by multiplying force’s previous year-end values by the total England and Wales change from the previous year to the current, excluding estimated values
2013	Surrey Police	Partial	As above
2014	Gwent Police	Partial	As above
2015	Bedfordshire Police Hampshire Constabulary	None	As above
2016	Bedfordshire Police Essex Police Leicestershire Police	None	As above
2016	Dorset Police	Partial	As above
2017	Kent Police	None	As above
2018	Kent Police	None	As above
2019	Hertfordshire Constabulary Kent Police	None	As above
2019	Lincolnshire Constabulary	Partial	As above
2020	Hertfordshire Constabulary Kent Police Lincolnshire Constabulary	None	As above
2021	Hertfordshire Constabulary Kent Police	None	As above
2022	Hertfordshire Constabulary Kent Police	None	As above
2022	Derbyshire Constabulary Lincolnshire Constabulary	Partial	As above
2022	West Midlands Police	Partial (for 9 months only)	25% of drug seizure quantities and preparation types between 1 April 2022 to 31 December 2022 have been estimated for, in addition to 100% of drug seizure quantities and preparation types between 1 January 2023 to 31 March 2023. Quantities, preparation type and drug codes were estimated using an extrapolation method by calculating the mean average of the partial data provided
2022	Surrey Police	Partial	Quantities, preparation type and drug codes were estimated by using an extrapolation method by calculating the mean average of the partial dataset provided
2023	Kent Police	None	Number and quantity of seizures estimated by multiplying force’s previous year-end values by the total England and Wales change from the previous year to the current, excluding estimated values

Table 3: 2022 to 2023 imputed data

Force	Total number of seizures (including imputed seizures)	% imputed	% of overall seizures made up of imputed seizures
Kent Police	4,548	100%	2%

As shown in Table 3, the Home Office imputed 100% of drug seizure data from Kent Police in year ending March 2023. The imputed seizures account for approximately 2% of the total number of drug seizures in the year ending March 2023 publication from police forces and Border Force.

1.4 Data revisions

Police forces can send revised data following a publication and it is the authors’ standard practice to incorporate revisions for previous years into the latest release. Corrections and revisions follow the Home Office Statement of Compliance with the Code of Practice for Statistics - Revisions and Corrections Policy.

Each release contains the most up to date figures; therefore, each subsequent release supersedes the previous one.

Cumbria revised their year ending March 2022 data, which is reflected within the year ending March 2023 publication.

1.5 Uses

Statistics on seizures of drugs are used for a variety of purposes, which are listed below using the standard categorisation for Official Statistics (UK Statistics Authority monitoring brief 6/2010, The Uses Made of Official Statistics.

• informing the general public’s choices:
  • about the state of the economy, society, and the environment: figures on drug seizures are used occasionally by the media in articles on the drug situation
  • about the performance of government and public bodies: figures on numbers and quantities of seizures are requested via Parliamentary Questions and Freedom of Information cases to gauge performance in general or specific areas
• government policymaking and monitoring: the primary use of the drug seizure statistics is by international agencies, for example, the United Nations Office on Drugs and Crime (UNODC), to compare performance nationally
• informing public marketing campaigns: drug seizure statistics are used in anti-drug campaigns by individual police forces or nationally
• supporting third sector activity – lobbying: drug seizure statistics are used by public safety lobbies to monitor current government legislation and government policy
• facilitating academic research: researchers into policing and criminology often use police statistics such as those on workforce and recorded crime. There is limited use of drug seizure statistics in academic research because drug seizures are not considered a measure of drug prevalence

1.6 User experiences

The Home Office conducted a survey for the Seizures of drugs in England and Wales statistical release for the year ending March 2014 so that the department could assess how well it met users’ needs and might make improvements where possible.

There were 11 responses to the survey. Key points included the following:

• most respondents were students, followed by those who worked in the voluntary sector; responses were also received from police forces, other government departments and other public organisations
• respondents who stated that they had not found the information they were looking for, sought data on specific drugs which are not currently included as individual drugs in the publication
• almost all respondents reported that they had used the data tables, over half reported they had used the main commentary, and half reported they had used the statistical news release; a third of respondents stated they had used the user guide; for those respondents that had used the tables, commentary and statistical news release, the majority reported that they were satisfied with them

1.6.1 Ongoing user engagement

In addition to carrying out surveys of users, the Home Office engages with users and stakeholders of the statistics on an ongoing basis to ensure the statistics remain as relevant as possible. These include police forces, Border Force, Public Health England, the Scottish Government, the National Crime Agency and European Monitoring Centre for Drugs and Drug Addiction. Working with these institutions allows us to share knowledge and ensure that our statistics continue to meet customers’ needs. The Home Office is consulting with stakeholders on this year’s publication, which can be accessed here. This survey closes 1st May 2024.

1.7 International comparisons

The Home Office has a statutory requirement to provide drug seizures data to the United Nations Office on Drugs and Crime (UNODC) annually, for publication in its annual world drug report. When considering data for different countries, it is worth noting that they may relate to different time periods or have been counted or recorded differently. As such, they may not be directly comparable with figures for England and Wales.

Data relating to seizures of drugs by police forces in Scotland are published by the Scottish Government. Similarly, the Police Service of Northern Ireland publishes statistics of its seizures. Please note that data collection methods and counting rules may differ between England and Wales, Scotland, and Northern Ireland.

1.8 Where are the latest published figures?

The annual Seizures of drugs in England and Wales publication, and other Home Office statistical releases, are available from the Home Office pages of the GOV.UK website.

1.9 Feedback and enquiries

We welcome feedback on Seizures of drugs in England and Wales. If you have any comments, suggestions or enquiries, please email them to drugseizures.datacollection@homeoffice.gov.uk.

Drugs Exploitation and Abuse Analysis Unit, 2^nd floor Peel Building, 2 Marsham Street, London, SW1P 4DF.

1.10 National Statistics status

These statistics have been designated as National Statistics, following an assessment by the UK Statistics Authority’s regulatory arm. The Authority considers whether the statistics meet the highest standards of Code compliance. These include the value the statistics add to public decisions and debate, and the highest standards of trustworthiness, quality and public value.

This statistical bulletin is produced to the highest professional standards and is free from political interference. It has been produced by analysts working in the Drugs, Exploitation and Abuse Analysis Unit in accordance with the Home Office’s statement of compliance with the Code of Practice for Official Statistics, which covers Home Office policy on revisions and other matters. The Chief Statistician, as Head of Profession, reports to the National Statistician with respect to all professional statistical matters. They oversee all Home Office National Statistics products with respect to the Code, being responsible for their timing, content and methodology.

2. Conventions used in seizures of drugs statistics

2.1 Rounding

Data is mainly provided unrounded in the data tables of Seizures of drugs in England and Wales. This is to promote transparency and allow users to exploit the data further.

However, caution should be taken when comparing small differences between time periods. The figures in the tables in this bulletin are generally shown to the last digit in order to provide a comprehensive record of the information collected.

The data tables are produced using R software and the function used for this publication, round(), rounds percentages to the nearest whole number, except for rounding .5 which is rounded to the nearest even number. For example, 23.5% would be rounded up to 24%, and 24.5% would also be rounded to 24%.

2.2 Use of symbols

The following symbols have been used in the tables:

• ‘0’ indicates amounts rounded to zero (this does not apply when amounts are presented to one decimal point), or nil amount

• ‘x’ indicates data not available

• ‘z’ indicates data not applicable

3. Coverage, drugs counting rules and conversion factors

3.1 Misuse of Drugs Act

The statistics in this bulletin and accompanying tables relate to the seizure of drugs controlled under the MDA 1971, which came into force on 1 July 1973, and substances controlled under the Psychoactive Substances Act (PSA) 2016, which came into force on 26 May 2016. The MDA divides drugs into 3 categories according to their harmfulness to the individual who misuses them, and to society. A full list of drugs in each category is given in Schedule 2 to the MDA 1971, as amended by Orders in Council.

The Home Office first collated drug seizure statistics in an electronic format in 1974. Until the publication in 2006, data originally covered the United Kingdom rather than England and Wales. Since the introduction of the MDA, there have been various changes to which drugs are covered and to recording practices by police forces and other agencies. As such, drug seizure statistics are not directly comparable from year to year and furthermore are not a measure of drug prevalence in society.

3.2 Classification of drugs

The MDA divides drugs into 3 categories – Classes A, B and C – according to the harm they cause to the user or to society when they are misused. Class A drugs are considered the most harmful. It is not feasible to publish detailed seizure statistics for every drug covered by the MDA. While all drugs are included in the totals, only those in the table below are covered in detail within this release.

Table 4: Drugs and their classifications under the MDA

Class A	Class B	Class C
Powder cocaine	Amphetamines1	Anabolic Steroids
Crack cocaine	Barbiturates1	Benzodiazepines
Ecstasy	Cannabis2	Temazepam
Heroin	Ketamine3
LSD	Mephedrone
Methadone	GHB4
Morphine

Notes:

1. Amphetamines and barbiturates are Class A drugs if prepared for injection.
2. Cannabis was reclassified from a Class B to a Class C drug in January 2004, and then classified back to a Class B drug on 26 January 2009.
3. Ketamine was reclassified from a Class C to a Class B drug on 10 June 2014.
4. GHB was reclassified from a Class C to a Class B drug on 13 April 2022.

3.3 Key changes in coverage

Table 5: Dates and changes of coverage

Date	Change
1 July 2003	GHB was classified as a Class C drug
29 January 2004	Reclassification of cannabis from a Class B to a Class C drug under the Criminal Justice Act 2003
18 July 2005	Raw magic mushrooms were classified as a Class A drug. Previously only prepared (such as dried or stewed) magic mushrooms were classified as Class A drugs
1 January 2006	Ketamine was classified as a Class C drug
18 January 2007	Methamphetamine (commonly known as ‘crystal meth’) was reclassified from a Class B to a Class A drug
26 January 2009	Cannabis was reclassified from a Class C to a Class B drug. For consistency, cannabis is listed under Class B for the entire time series shown
23 December 2009	Gamma-Butyrolactone (GBL), 1, 4 – Butanediol, Oripavine and Benzylpiperazine (BZP) became Class C controlled drugs
16 April 2010	Mephedrone became a controlled drug (Class B). Other cathinone-based substances also became Class B controlled drugs, though some were already controlled as Class C drugs
28 March 2011	Tapentadol (Class A) and amineptine (Class C) became controlled drugs
13 January 2012	Phenazepam (Class C) and pipradrol-related compounds (Class B) became controlled drugs
10 June 2014	Ketamine was reclassified as a Class B drug. For consistency, ketamine is listed under Class B for the entire time series shown
26 May 2016	Psychoactive Substances Act (PSA) 2016 is introduced
2 December 2016	‘Third generation’ of synthetic cannabinoids were brought under control as Class B drugs
1 April 2019	Pregabalin and gabapentin were brought under control as Class C drugs. A delay in updating the drug recording codes means that some pregabalin and gabapentin seizures may have been omitted from the records for year ending March 2020
13 April 2022	Gamma-Hydroxyburtyric Acid (GHB), Gamma-Butyrolactone (GBL) and 1,4-Butanediol (1,4-BD) were reclassified from Class C to Class B on 13 April 2022

3.4 Psychoactive Substances Act 2016

Seizures of NPS have been included in the releases for years ending March 2018 to March 2023. Due to the large number of different NPS in existence, it is not feasible to report on all individual NPS substances. They have therefore been grouped into 4 main categories – nitrous oxide, synthetic cannabinoids, NPS powder, and other NPS (including pills). Synthetic cannabinoids are counted within ‘Other Class B’ seizures, given that the ‘third generation’ of synthetic cannabinoids were controlled as Class B drugs in December 2016.

Up to and including the 2022 to 2023 report, data on NPS seizures were designated as experimental statistics, as they were not fully developed and did not meet the rigorous quality standards of Official Statistics.

For clarity:

• NPS and synthetic cannabinoid seizures continue to be reported in Appendix Tables 1 and 2
• where forces have seized nitrous oxide, NPS powders and other NPS drugs only (and no other drug types), these seizures have been excluded from all tables apart from Appendix Tables 1 and 2
• synthetic cannabinoid seizures have been included in figures for Other Class B drugs, and also reported in Appendix Tables 1 and 2
• fentanyl and fentanyl analogue seizures have been included in figures for Other Class A drugs, and also reported in Appendix Tables 3 and 4

3.5 Drugs counting rules

A single seizure is where only one drug is seized on a particular occasion (for example, powder cocaine).

A multiple seizure is where 2 or more drug types (for example, heroin and powder cocaine) are seized on a particular occasion. The occasion is counted once in the total number of seizures, but a seizure is counted against each individual drug type and drug class involved.

Example: A seizure is made of powder cocaine, cannabis resin and herbal cannabis. This seizure would be counted as:

• total seizures: one seizure in the overall total for the number of seizures by that agency
• drug type: one seizure of powder cocaine, one seizure of cannabis resin, one seizure of herbal cannabis and one overall seizure of cannabis
• drug class: one seizure of Class A and one seizure of Class B

3.6 Purity of seized substances

Prior to the year ending March 2012, the National Statistics on drug seizures were supplemented with data provided by the Forensic Science Service (FSS) on the purity of drugs seized (these data were not National Statistics). Data for the year ending March 2012 onwards is not available due to the managed closure of the FSS.

UK Focal Point on Drugs collects and publishes purity data for reports by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) and the United Nations Office on Drugs and Crime (UNODC).

3.7 Coverage by agency

Seizures from joint operations involving Border Force and the police are recorded against the lead agency that takes possession of the seized drugs.

3.7.1 Border Force

UKBA was launched in April 2008, creating a new frontline operation formed of the Borders and Immigration Agency, UK Visas, and staff from His Majesty’s Revenue and Customs (HMRC) employed at the frontier. As well as retaining responsibility for the inland control of illicit goods such as cigarettes, tobacco and alcohol, HMRC officers retained the legal power to seize drugs if discovered while they are conducting their inland duties. Consequently, for the years up to and including year ending March 2011, data for UKBA included a few drug seizures possibly attributed to HMRC.

Following the publication of the Vine Report (February 2012) which investigated unauthorised border checks, the Home Secretary split the Border Force and UKBA into separate organisations. This came into effect from 1 March 2012. From the year ending March 2013 edition, the Home Office’s statistical bulletin on the Seizures of drugs in England and Wales refers to Border Force seizures rather than UKBA.

For the year ending March 2012 onwards, UKBA / Border Force figures include seizures made offshore, and which have been attributed to the nearest port (within England or Wales only) on their recording system. These include only those seizures made by its fleet of ongoing sea-going patrol vessels (cutters) that operate around the UK coastline; seizures made overseas by juxtaposed controls are excluded. For the years ending March up to and including 2011, seizures made by cutters were excluded.

Home Office analysts work closely together with Border Force to ensure that its statistics fully comply with the Code of Practice for Official Statistics. A breakdown of Border Force figures contained in Seizures of drugs in England and Wales are published each quarter, within its quarterly compilation of performance information. The drug seizure figures are based on the same counting rules used to compile Seizures of drugs in England and Wales, and quarterly figures relating to Border Force seizures in England, Wales, Scotland and Northern Ireland are presented separately.

3.7.2 Serious Organised Crime Agency (SOCA) and National Crime Agency (NCA)

Seizures by SOCA have not been identified separately in this report because most of its domestic seizures are made with local police forces, with the seizure attributed to the police. It should be noted that many SOCA seizures are attributed to local police forces when operations have been run together.

In October 2013, the NCA was established, replacing many of the functions (including drug seizures) of SOCA.

3.8 Conversion factors

The quantities of drugs seized are summarised in terms of kilograms, doses or plants (for cannabis plants only). Most drugs can plausibly be seized in a preparation form other than kilograms or doses. Therefore, in order to present all seized quantities within a given drug type in terms of one comparable unit (either kilograms or doses), conversion factors are applied to estimate the overall quantity of drugs seized.

Conversion factors were revised from the 2005 publication to reflect trends in average drug preparations. These have been used for the annual Seizures of Drugs in England and Wales publications since year ending March 2007.

Prior to year ending March 2023, nitrous oxide seizures in kg or litres by Border Force were excluded from the publication. However, from year ending March 2023 the publication reports nitrous oxide using a new conversion factor in order to capture all preparation of nitrous oxide. This conversion factor has been used to revise all quantities of nitrous oxide seized by Border Force for all previous years.

The conversion factor assumes 1 dose/cannister of nitrous oxide equates to 8g, which equates to 4.1 litres.

For Border Force’s data in Summary Tables 3b and 3c, and Supplementary Table 2, quantities requiring conversion are not included in the breakdowns, although they are included in the total estimated quantity (kilograms or doses).

Glossary

Amphetamine– a stimulant drug controlled within Class B of the Misuse of Drugs Act (MDA) 1971.

Anabolic steroids – a drug within Class C of the MDA used to enhance sporting performance and muscle building.

Barbiturates – a highly addictive relaxant drug, controlled within Class B of the MDA.

Benzodiazepines – group of drugs that are minor yet addictive tranquillisers and controlled under Class C of the MDA.

Border Force – responsible for frontline border control operations at air, sea and rail ports in the United Kingdom. In this release, Border Force seizures relate to those found in the land territory of England and Wales only.

Cannabis – a relaxant drug also known as marijuana, controlled within Class B of the MDA.

Cannabis plants – live plants often seized from a cannabis ‘farm’.

Cannabis, herbal – dried leaves and flowers of cannabis plants, usually chopped and dried.

Cannabis resin – cannabis in the form of solid, brown lumps. Often rolled with tobacco and smoked.

Class A, B, C – classification of drugs as listed in part I, II and III of Schedule 2 of the MDA. The classification determines the legal sanction (for example, maximum sentence) with Class A attracting the most severe and Class C the least.

Powder cocaine – a powerful, addictive stimulant drug, controlled within Class A of the MDA. Included here is cocaine in powder form, see Crack cocaine for further details.

Controlled drug – chemical substances listed in the MDA. Unauthorised possession and supply of these drugs are illegal. Some controlled drugs are used as medicines, and the MDA allows certain authorised people, such as researchers or doctors, to use them in research or prescribe them to patients.

Crack cocaine – cocaine in ‘rock’ rather than powder form, controlled within Class A of the MDA.

Drug – when used in this release, it refers to a controlled drug.

Ecstasy – also known as MDMA, an acronym of its chemical name, it is a stimulant drug, controlled within Class A of the MDA.

Fentanyl – a powerful synthetic opioid similar to morphine and a painkiller, controlled within Class A of the MDA.

Financial year – the 12 months ending on 31 March.

Gabapentin – a prescription-only medicine used to treat epilepsy and neuropathic pain, controlled within Class C of the MDA.

GHB – Gamma-Hydroxybutyrate, an anaesthetic drug, controlled within Class B of the MDA.

Government Office Region (GOR) – the Government Office Regions have been the primary classification for the presentation of regional statistics, although the regional government offices were closed in 2011. There are 9 GORs in England: North East; North West; Yorkshire and the Humber; East Midlands; West Midlands; East of England; London; South East; and South West. In this report, analysis by region also includes separate analysis for Wales.

Heroin – a highly addictive drug made from morphine, a relaxant and strong painkiller. Usually injected by users and controlled within Class A of the MDA.

Ketamine – a powerful anaesthetic drug often inhaled, can be hallucinogenic, controlled within Class B of the MDA.

LSD – lysergic acid diethylamide, or ‘acid’, a powerful hallucinogenic drug controlled within Class A of the MDA.

Methadone – a synthetic opiate (that is, from opium poppies) manufactured for use as a painkiller and as a substitute for heroin in the treatment of heroin addiction, controlled within Class A of the MDA.

Mephedrone – a powerful stimulant (sometimes called ‘meow meow’) and is part of a group of drugs closely related to amphetamines, like speed and ecstasy. Mephedrone is controlled within Class B of the MDA, unless seized in an injection form whereby it is controlled within Class A.

Misuse of Drugs Act (MDA) – 1971 Act that legislates against the unauthorised possession and supply of controlled drugs. Reference to the MDA in this release covers the original Act and subsequent amendments and modifications.

Morphine – an addictive opiate, a relaxant and painkiller, controlled within Class A of MDA.

New psychoactive substances (NPS) – drugs that mimic the effect of existing drugs such as cannabis, ecstasy and powder cocaine. Some NPS are controlled under the MDA, while other NPS are illegal to supply, produce and import under the Psychoactive Substances Act 2016.

Nitrous oxide – a colourless gas, also known as ‘laughing gas’, which can be misused for its psychoactive effects by inhalation. Nitrous oxide was controlled by the Psychoactive Substances Act 2016 up until November 2023 when it was classified as Class C under the MDA. Therefore, for the purposes of the year ending March 2023 publication, nitrous oxide is included under psychoactive substances.

Police officers – employees of a police force, who have taken an oath (under the Police Act 1996) to uphold the law.

Population figures – some tables and graphs in this release use population figures to calculate the total number of drug seizures per million population. The population figures used for the year ending March 2015 statistics are mid-2014 population estimates based on the 2011 Census, provided by the Office for National Statistics.

Pregabalin – a prescription-only medicine used to treat epilepsy, neuropathic pain and anxiety, controlled within Class C of the MDA.

Psychoactive substance – any substance intended for human consumption that can produce a psychoactive effect.

Psychoactive Substances Act (PSA) – 2016 Act that created a blanket ban on the production, distribution, sale and supply of psychoactive substances in the United Kingdom for human consumption.

Seizure of drug(s) – a discovery and confiscation of a substance or substances that, after testing, are found to be controlled drugs. Not all drugs included in the seizures have been ‘seized’ in the strictest sense of the word; for example, a member of the public may hand in to the police what appear to be drugs found in the street. These items will be recorded at individual police stations and then destroyed.

Synthetic cannabinoids – a class of NPS designed to replicate a similar effect to cannabis.

Temazepam – minor yet addictive tranquilliser, controlled within Class C of the MDA.

Temporary Class Drug Order (TCDO) – a facility under the MDA to trial a substance as a controlled drug for up to 12 months until a decision is made whether to introduce it substantively.

For more information about these and other controlled drugs, please refer to the Frank website.

Appendix A: Key stages in the production of the statistical release

A. Preparatory work

• Annual Data Requirement (ADR) process (during the 12 months prior to the data period)
  • consultation with forces and stakeholders; all stakeholders complete a questionnaire to justify the retention (or otherwise) of each of their series
  • requests for changes or additions to the ADR considered by the ADR committee (which weighs up the benefits against administrative burden)
  • ADR committee decisions for inclusion in the final ADR for submission for Home Secretary’s approval
• Review of IT systems (during the 12 months prior to the data period)
  • incorporate any amendments, additions and/or withdrawals
  • any case for IT work incurring costs to be justified and approved by budget manager
• Issue statistical returns, covering letter and notes for guidance to police forces (around the start of the data period)
• Agree and pre-announce the provisional date of publication of the statistical bulletin on the Office for National Statistics (ONS) publication hub. Please refer to the Code of Practice for Statistics updated May 2022. Section T3.1 states: ‘The release of both regular and ad hoc Official Statistics should be pre-announced through a 12-month release calendar, giving the specific release date and time at least 4 weeks in advance where practicable’
• Review content of the statistical bulletin and other regular outputs (around 6 months prior to publication), then agree findings with stakeholders. Any substantial reduction in content of statistical release would require a consultation with users
• Review and update project plan for the new financial year (around 6 months prior to publication):
  • include all the milestones in this framework, plus deadlines and measures of criticality (for example, a traffic light system)
  • timings to fit in with staffing levels, pressures and the relative priorities of each series
  • timings also to fit in with National Statistics pre-announced months of publication (with no series to be published later than 12 months after the data period) and policy demands

B. Data input and quality assurance

1. Police forces’ submission of returns within deadline:
   • data collection section deals with force queries on completion of return, with support from output team where required
   • output team deals with all other queries about notes for guidance, definitions, release practice and recording practice
   • data collection section logs and ensures that returns are correctly input electronically
2. Figures for police forces are reviewed to see if data is suitable for publication. If not, or if data cannot be supplied, any data supplied by that force will need to be excluded from the publication, and estimated instead, (see section 1.3, Imputation of data). This is only done as a last resort, and with the agreement of the respective police force. The drug seizure data collection is part of the ADR, and police forces have a statutory requirement to submit the data requested.
3. Validation and variation checks, and review of any issues identified, with the forces. These checks are a combination of automated error checks and analytical checks, from forces’ data extracted from the database. They are focused on the key drugs and quantities seized (for example, all notably large drug seizures are checked with police forces before publication). Prior to 2021, these checks were carried out in Microsoft Excel, using extracts of data from the database, but from year ending March 2021 onwards, the checks have been produced automatically, using R code. From the results of these checks, analysts produce summaries of the key issues in the data, for review and discussion with the respective forces.
4. Receipt and input of revised returns following validation checks, and satisfactory reasons or revisions provided following variation checks.
5. Data confirmation exercise. Each police force is sent a report containing data in a format similar to the format in the publication. Like the data checks in point (3), these were previously produced in Microsoft Excel, but are now generated using R software, then exported to Microsoft Excel for formatting to improve the quality and consistency of the reports. Forces are then asked to provide written confirmation that they agree with the figures that will be published. This is to reduce further the risk of incorrect figures being released and supports the Home Office in any disagreement with a police force over the figures published for that force.
6. Receipt and input of revised data where appropriate following the data confirmation exercise.
7. Production of complete validated dataset following all data being signed off by police forces.

C. Preparation for publication

1. Prepare detailed publication schedule (at least 3 months before publication), containing all specific tasks, milestones and analysts allocated to them.
2. Agree and pre-announce finalised day of publication (around 1 to 3 months before publication).
3. Prepare draft of tables, charts and commentary and circulate to nominated people for quality assurance, 2 to 3 weeks before publication. This group appears on the pre-release access list.
4. Send statistical news release and pre-release access for preparation of web pages.
5. Circulate the commentary, tables, charts and statistical news release, 24 hours before publication, to a nominated list of people (including ministers and press office) as shown on pre-release access list.
6. Meet with Home Office colleagues on 24-hour list to discuss content and handling issues.
7. Publication.

D. Follow-up work

• Wash-up meeting on process of publication
  • agree actions for next year and lessons learned
  • consider any information that could be sent back to police forces to aid their processes
• Published dataset to be used for Parliamentary Questions, Freedom of Information and other enquiries (until following publication)