TSEM9916 - Ownership and income tax: Specific types of property: land and buildings - joint ownership
A maximum of four persons can be registered as legal owners in the register of land (S34 Trustee Act 1925).
When property is held jointly, there is a presumption in law that the property is held as joint tenants (TSEM9210).
Where property is purchased for investment purposes it is likely that a joint tenancy will be rebutted by evidence that the investors wanted their investment to pass under the terms of their will in the event of death rather than to the surviving owner/s.
Land Registry form TR1(TSEM9910) provides a box for joint-transferees to declare whether they are to hold the property on trust for themselves as joint tenants, or on trust for themselves as tenants in common in equal shares, or on some other trusts which are inserted on the form. If this is complied with, you can accept what it says. (The transfer will be valid whether or not this part of the form is completed.)
The Land Registry provides guidance on joint ownership: Land Registry Public Guide 18 Joint property ownership