Landlord Law

4.2.2. Proceeds of crime

4. Property management
4.2 Financial management
4.2.2 Proceeds of crime
You must report any suspicion that another person is engaged in money laundering or other related financial crime to the National Crime Agency (NCA) before proceeding with any transaction with that person.

Money laundering activities are fairly common in the property industry so you need to watch out for thie.

The NCA website is here.