UK Landlord Forum / Life

I have a tenant with a one year tenancy agreement dating from end-Jan. 2010. Because the annual rent was more than £25,000 this was not an Assured Shorthold Tenancy. On October 1, the upper threshold on Assured Shorthold Tenancies was raised. Does this mean that the existing tenancy agreement automatically becomes an Assured Shorthold Tenancy?
(This is important because he is 5 months in rent arrears and I want to repossess my flat.)