Do I need to provide a new tenancy agreement?

Other

I am in the process of completing the purchase of a propery that already has a tenant. I'd like to keep the tenant on and rent the property to him as he is now. I have seen the tenancy agreement between the current tenant and the current owner, but will this agreement still be valid when I am the new owner, or do I have to create a completely new tenancy agreement?

Thanks,

Ed.