The correct course of action would be to revoke the hotel's operating licence until the Priory condition has been fulfilled (possibly with a fine as well). That would cause FK problems but might also make him even more obstructive where the stadium is concerned - if that's possible!
Interesting that Bob Price indicated that OCC owned the Priory after the agent said they didn't. Presumably OCC are the owners, in which case do they have to give permission for any sub-let? If so, my guess is they'd be less inclined to permit a sub-let while a planning condition breach has not been resolved.
Interesting to see how this one plays out. As an aside, it was OCC's decision not to allow the marquee that put the previous landlord in an untenable position and probably made the pub unprofitable for anyone else to run.