Potential Problem Tenant

Tenancy Deposits

On the 9th June we rented a flat to one individual as the tenant needed to move quite quickly the cleaning of the flat was delayed until the day after the tenancy commenced, the tenant was fine with this. When our cleaner arrived at the flat there were two other people in the flat but not the tenant who signed the agreement, There did not seem to be an explanation from the two people who were present and we have tried unsuccessfully to contact the tenant. He has signed the agreement but we have not banked his money - where do we stand legally - references were carried out and all seemed to be in order. We are just concerned that he may of rented it out for someone else.