London Transport, everything from taking care when you step off a bus in the dark to calling out the names of stations and stops on train and bus roots (impossible to see when windows were blacked out). A 1943 campaign to promote the idea of people standing on the right of escalators offered a £10 prize for adding further lines to the couplet "Here's another bright suggestion / Standing RIGHT prevents congestion." The winner added, "On the right it's 'Stand at Ease' / On the left it's 'Quick March,' please."
After publishing cartoons in the staff magazine he began to send out his work to other publications, selling to Time and Tide and the Sunday Referee before breaking into Punch in 1937. He was the magazine's most prolific contributor over the next few years and a collection of his cartoons appeared as early as 1941.That same year Langdon, having served as an Executive Officer with the London Rescue Service, joined the R.A.F. as a pilot officer. He became a Squadron Leader in 1945 but spent his time as a cartoonist and edited the Royal Air Force Journal in 1945-46, where he continued to feature Billy Brown.
He continued to work for the Sunday Mirror until 1990 and for Punch until it closed in 1992. He was awarded the OBE in 1988 and elected FRSA that same year. He was given the Lifetime Achievement Award by the Cartoon Art Trust in 2001.
His books included Home Front Lines, 1941; All Buttoned Up, 1944; Meet Me Inside, 1946; Slipstream (with R. B. Raymond), 1946; The Way I See It, 1947; Hold Tight There!, 1949; Let’s Face It, 1951; Wake Up and Die (with David Clayton), 1952; Look at You, 1952; All in Fun, 1953; Laugh with Me, 1954; More in Fun, 1955; Funnier Still, 1956; A Banger for a Monkey, 1957; The Puff and Wuff Adventure Book, 1957; Langdon At Large, 1958; I’m Only Joking, 1960; Punch with Wings, 1961; How to Play Golf and Stay Happy, 1964; David Langdon’s Casebook, 1969; How To Talk Golf, 1975; Punch in the Air, 1983; and Soccer—It’s a Funny Old Game, 1998.
Obituaries: The Guardian (23 November), The Independent (2 December), Daily Telegraph (8 December).