Illustration of Trench Strafing, First World War, (c1920). 'British low-flying scouts co-operating in an infantry attack on the Western Front'. Biplanes shooting at Germans in the trenches.

An S.E.5a (left) and a Sopwith Camel strafe German trenches as the prelude to a British ad-vance in late 1917. Fighter pilots, who were fair game for every enemy holding a gun, considered it a “dirty job,” but it increasingly became a regular part of their duties. (Branger/Roger VIollet, FPG, Print COllector, Corbis (Getty Images))

Branger/Roger VIollet, FPG, Print COllector, Corbis (Getty Images)