John Seddon was born near Wigan on 29 September 1915. He was educated at Leeds Modern School then Leeds University where he was awarded a First in Mathematics (BSc 1937) and obtained a PhD in 1939. In 1940 he married Barbara Mary Mackintosh with whom he had one son and two daughters.

In 1939, Seddon joined the wind tunnel section at the Royal Aircraft Establishment (RAE) at Farnborough as a Scientific Officer. He specialised in the aerodynamics of engine cooling systems and improved the performance of fighters and bombers (including the Spitfire, Typhoon, Stirling, Lancaster and Mosquito).

In 1955, Seddon was awarded a Harkness Fund Fellowship and went to the California Institute of Technology where he researched shock wave boundary layer interactions. From 1956-1959, Seddon was Head of Experimental Supersonics at the RAE, Farnborough and moved to the RAE at Bedford as Superintendent of the Tunnels II Division (1959-1966) where his work contributed to the development of combat aircraft. From 1966-1968, Seddon was the Director of Scientific Research (Air) at the Ministry of Technology rising to the position of Director-General of Aircraft Research at the Ministry of Defence (a position he held from 1969 until his retirement in 1975). After his retirement, Seddon acted as a consultant to several companies and organisations including: Westland Helicopters (1976-1984) and Rolls Royce (1985-1986). He was a senior research fellow at Bristol University (1976-1982) and a visiting professor at Nanjing Aeronautical Institute in China and at the Middle East Technical University in Turkey.

Seddon was closely involved with the Anglo-French development of Concorde and also worked on the Spey engine intake for the Phantom fighter.

Publications: Intake Aerodynamics (with E. L. Goldsmith), 1985; Basic Helicopter Aerodynamics, 1990; papers on air intakes and other aerodynamic subjects, in ARC Reports and Memoranda Series and other scientific media.

Seddon died on 13 July 1991.