The Firefly was a private-venture design, penned by Marcel Lobelle. A completely new design, it shared little with the Firefly I beyond the name. Making use of experience gleaned from the earlier machine, it was developed in response to Specification F.20/27 for a single-seat interceptor. It first flew on 5 February 1929.
The Firefly II competed for the RAF contract against the Hawker Fury, showing superior speed but was criticised for having heavier controls. Crucially, it retained a mainly wooden structure despite the Air Ministry's demands for metal structures. This led to the Fury being selected. Afterwards, the prototype was rebuilt and renamed Firefly IIM, the "M" denoting the all-metal construction of the rebuilt machine.
A revised prototype with longer-span wings, the Firefly III was built to Specification N21/26 as a carrier-based fighter to replace the Fleet Air Arm's Fairey Flycatchers, first flying on 17 May 1929. Like the land-based fighter, it was rebuilt with more metal components as the Firefly IIIM, and again like the Firefly II, was beaten by a design produced by Hawker, in this case the Hawker Nimrod. Although no production orders ensued, the Firefly IIIM was fitted with floats and used as a trainer by the RAF's High Speed Flight preparing for the 1931 Schneider Trophy race.