How do mean 'specialised!? Amongst the designs that tendered for the Spec. were three twin engined - Bristol 153a, Westland and Supermarine; and five single engined aircraft - all to be with wing mounted cannon - Bristol 153, Boulton-Paul P.88a (Hercules) and P.88b (Vulture), Hawker and Supermarine. The Air Ministry wanted five prototypes - 2 Westland, 1 Supermarine (twin), and 2 Boulton-Paul. But the Treasury only would allow one type. Having the P.88 (I prefer the 'A') in the air earlier gives the RAF more time to sort out the problems of the cannons in the wings.