The success of the three-seat, high-wing de Havilland Leopard Moth, introduced in 1933, had proved that there was a market for this class of aircraft.
[3] The designer of the Pirate was the experienced Harold Boultbee, who had recently produced the Civilian Coupé, and construction began early in 1935.
The folding mechanism was unusual: unlocked, the wings slid forward and tipped leading edge down, so that when the front spar was released from its fitting the wings could fold rearwards and downwards about the rear spar.
The main undercarriage oleo legs were attached close to the fuselage end of the lift struts.
Ahead of them, the Niagara, under a characteristically neat Pobjoy cowling with "helmet" exhaust ports drove a two-bladed propeller.