Are all contracts the same in regards to loss of bonuses for requesting to leave? For the sake of £1.5m I'd imagine that any potential purchasers would simply cover that for him - after all, if he hands in a request his value would drop by more than £1.5m anyway so the bidder wouldn't exactly be out of pocket. The type of clubs that would want him won't baulk at paying £1.5m on top to get their man.
That said, IF there is this mythical release clause, then the player doesn't need to request to leave.