Tony Gaze of 610 Squadron driving his MG around the perimeter track of Goodwood in 1941 lead to the idea of its use for post-war racing.

many pilots purchased their own 1930s MG Midget, but getting fuel was often a problem due to wartime rationing, so the pilots tapped into the available supply of avgas.

https://www.goodwood.com/sports/flying/latest-news/pilots--their-cars/