Forfeiture clause in an AST

Other

I am in the process of remortgaging my buy to let property which is a freehold property let on an AST for the last 5 years. The Lender has now come back asking " There are no forfeiture clauses in favour of the mortgagee so can you please let us have a revised Agreement signed by all parties as soon as possible.''
I understand that there are forfeiture clauses for Leasehold or Commercial properties but I have never encountered this for an AST agreement. Surely any such clauses would be detrimental to the tenant who has been excellent and would be classed as one with a Binding Tenancy under the buy to let mortgage should the lender have to repossess the property. By inserting a forfeiture clause now and creating a new tenancy does not seem to be morally correct but is it legally correct for the lender to insist on it?