Transfer Arrears to new Tenancy Agreement

I have a tenant who is £1500 in arrears. Rent payable £480 per month in advance. We have no tenancy agreement and I have an unsecured deposit of £400. The tenant had some huge personal problems last year that gave rise to the debt.
This is a little'out of the frying pan and into the fire' but if we set up a new tenancy agreement effective from say 1st April, would I be able to use that agreement to help me recover the £1500? after securing the deposit of course.