Frederick William "Gunner" Hill (24 February 1889 – 10 November 1959) is best known for his pre-war calculations that showed that the high speed fighters then being developed (notably the Supermarine Spitfire and Hawker Hurricane) would need to be armed with eight machine guns in order for them to be effective weapons.

He made key contributions to the development of the GM2 reflector gunsight that helped the allies gain air superiority over Germany.

He received his commission in August 1915 and was appointed as Assistant Experimental Officer at the Isle of Grain seaplane base where he invented two sights for aerial guns.

However, his position was eventually made permanent (at a lower salary) and he joined the staff of the Armament Research and Development Section of the Air Ministry.

A long series of air firing trials were carried out between 1931 and 1933 which produced large amounts of data that had to be analysed and summarised by Hill.

[18] The results produced were of sufficient quality to enable him to start making predictions about what might happen in actual combat under varying conditions of range and accuracy of sighting.

The conclusion of Hill’s analysis was that future fighters would need to carry no less than eight machine guns each capable of firing at least 1,000 rounds a minute.

[20] These were generally accepted and a properly constituted Air Fighting Committee (“AFC”) was set up, holding monthly meetings from 1 November 1934 with a place for the Assistant Director of Armament Research and Development and with Hill as the most junior member.

The future tactics of the RAF were worked out by this Committee, which is credited with instigating the multi-gun fighter specification leading to the Hurricane and Spitfire, the adoption of the reflector gunsight and the mechanically driven gun turret.

Hill carried out various tests and trials for the AFC including on armoured glass requested by Dowding which was later fitted to fighters.

Keith records that he sent Hill to France to investigate a mystery weapon that was claimed to bring down power lines.

[25] In 1939 the Armament Research and Development at the Air Ministry moved to Farnborough and worked with the Royal Aircraft Establishment (RAE).

He recognised the need for a scientist to explain some of the stranger ballistic effects that were appearing as fighter speeds increased and arranged for Hill to be transferred from Farnborough, initially for a limited time.

Hazel (1920–2010) was only 13 when she helped her father Frederick to calculate how many guns the new generation of Spitfires and Hurricanes would need to have, to bring down enemy aircraft.