At the start of the war, the principal British carrier-borne dive bomber was the Blackburn Skua, the Royal Navy's first operational monoplane . Like most British naval aircraft, it had lackluster performance but was nevertheless used extensively during the first two years of the conflict with decent results especially during the Norway campaign. Skuas were the first British aircraft to shoot down a German plane, a Do 18 over the North Sea; they also sank the cruiser Königsberg in Norway and participated in the attack on the French fleet at Oran. Eventually Skuas were replaced by Fulmars and were relegated to secondary duties like target towing and training. A similar development, the Blackburn Roc, was planned as a turreted fighter similar to the Defiant. In the event, however, the weight of the turred slowed down its performance and it was retired from service even earlier than the Skua.

The prototype flew for the first time on 9 February 1937 and was designated Skua Mk. I. However, production aircraft were of the Mk. II variety with uprated engines. No further variants were produced besides a spin-off fighter called the Blackburn Roc Mk. I which utilized the same power turret configuration as the Defiant. It was considerably less successful as it never served from carriers and was promply relegated from front-line service.