Gaining possession of flat

Tenancy Types and Management

It states that "The defendant give the claiment possession of flat on or before 30 November 2006"

My problem is that for the last four months the tenant has not been in the flat. The only contact I had was through his mobile phone. Initally I contcted him through his mobile for the due rent. once he was about six weeks in arrears he stopped answering his phone. I have left several messages for him to contact me but, he has not responded. As a matter of fact he has deserted the flat. The other tenants in the building used to see him while he was using the flat and they also say that they have not seen him for a length of time.

In the flat he has very little personal belongings, hardly any clothing and the flat is in a very messy state.
Please advice me as, how to gain possession of the flat in order to re-let it and what to do with his personal belongings. The tenat is already four months in rent arrears.
Thanking you
Sinbad