No rent and no communication from tenant

Tenancy Types and Management

A tenant moved into a property of mine on 10th May 2007 on a six-month AST (an RLA AST). He paid two months’ rent in advance. He was slightly late paying the rent due on 10th June, but paid in full. He was then two weeks late paying the rent for 10th July. Now I haven’t received any rent that was due on 10th August. I have called him numerous times, sent texts, written a letter and then dropped in this afternoon, leaving a hand-written note. He seems to have disappeared off the face of the earth! I will issue a section 21 to him before 10th September. But is there anything else I can do? And how to reclaim any lost rent?

Thanks