The company mainly built and modified aircraft under contract to other manufacturers, but had a few notable designs of its own, such as the Defiant fighter and the Balliol trainer.

After World War I, Boulton & Paul made their mark with the introduction of powered and enclosed defensive machine gun turrets for bombers.

The subsequent Overstrand bomber featured the world's first enclosed, power-operated turret, mounting a single Lewis gun and propelled by compressed air.

[2][page needed] This gave access to a large skilled workforce on top of the 600 or so employees that left Norwich for Wolverhampton.

This was followed by Boulton Paul's most famous aircraft, the Defiant, which was a revolutionary but flawed concept specified by the Air Ministry – a "fast" fighter with no fixed forward armament but a powerful four-gun dorsal turret at a time when most interceptors had only two machine guns.

In the jet age, Boulton Paul worked on the English Electric Canberra and de Havilland Vampire.

Boulton Paul's designs were largely based on originals licensed from the French company Société d'Applications des Machines Motrices [fr] (SAMM), while Nash & Thompson designs originated from the firm's co-founder, Archibald Frazer-Nash (and were known by FN designations)[citation needed] Boulton Paul's turrets were electro-hydraulic in operation; electric motors located in the turret drove hydraulic pumps that powered hydraulic motors and rams.

This was more effective than electric motors alone, and did not require hydraulic power developed by pumps on the aircraft's engines system utilized by the Nash & Thompson design.