Developed from the earlier Jupiter engine, later variants could produce 800 horsepower (600 kW) from its capacity of 1,500 cubic inches (25 L) by use of a geared supercharger.

Although the Mercury initially failed to attract much interest, the Air Ministry eventually funded three prototypes and it became another winner for the designer Roy Fedden.

The smaller capacity engine was then boosted back to Jupiter power levels, while running at higher rpm and thus requiring a reduction gear for the propeller.

[5] The Aircraft Restoration Company based at Duxford Airfield also operate a Mercury powered Westland Lysander (G-CCOM) as well as a Bristol Blenheim I (G-BPIV) light bomber fitted with two Bristol Mercurys, which can be seen at air displays at IWM Duxford as well as across the UK.

[6] The Fighter Collection, also currently based at Duxford Airfield, operate a 1939 Gloster Gladiator II (G-GLAD) powered by a Bristol Mercury XX.

[7] The Canadian Warplane Heritage Museum has a Lysander IIIA in flying condition as does the Vintage Wings of Canada.