My housemate is stealing from me. What can I do?Beta*

Theft is a police matter, so report it and get a crime reference number. A lock on your bedroom door needs the landlord's permission, but it's a reasonable request. Keep receipts and photos of valuables. Whether the landlord can remove your housemate depends on the type of tenancy. If you are all on one joint tenancy, the landlord can't evict just one of you, and you can't evict each other. If each of you has your own room contract, the landlord can take action against that person. Tell the landlord in writing what is happening.

Sources: Shelter: problems with people you live with