[3] The first prototypes were powered by a derated 325 shp Blackburn Turbomeca Turmo 600, a free turbine engine allowing clutchless transmission.

[1] Three more developed P.531-0s followed and these were delivered to the Royal Navy's Fleet Air Arm for trials and familiarisation.

Following evaluation by the Navy a batch of 30 developed aircraft were eventually ordered as the Westland Wasp.

The vision was improved with perspex panels in the doors, tankage was increased and all-metal rotors introduced.

Another P.531-2 was built for evaluation by the Indian government[4] but following a lack of interest was re-worked as Scout standard for the Army Air Corps.