Belgium Wishes To Buy Calais

We have just received an interesting offer from the Belgian delegation. They have expressed an interest in buying Calais from us in a bid to "reunite their historical territories". The sum they have proposed is quite high, and would certainly go some way to improving our own economy, the question is whether we believe this loss of land is worth that price. It should also be noted, that their diplomats did imply an escalation in tensions should we reject their offer.