 The first batches of MK I Wallaces were conversions of Wapitis, a total of 68 powered by 570 bhp (425 kW) Pegasus IIM3 engines.Westland designed an improved version, the Mk II which was fitted with a more powerful engine and the then-novel idea of an enclosed canopy over both crew positions.This offered greater comfort for the crew and improved the rear gunner's aim by protecting him from the slipstream.