Restrictive practice condition imposed by seller

I am interested in purchasing a property which is currently trading as a
public house with restaurant and letting rooms. The current owner is a pub
chain and are insisting that the sale is on the basis that the premises are
not used to sell or dispense alcohol, i.e. will not be licenced in any way.
I believe this is unreasonable and must somehow fall under the auspices of
restrictive trade. Is this "condition" legal and enforceable ? Thanks for
your consideration

They can ask you agree contractually.

but they may not be able to bind and party you sell to...