David was the youngest of the three sons of Wilfred Watkinson (1877-1944, born Wilfred Watkinson Holtzmann), doctor of medicine, and Violet Harwood Casson (1883-1928), daughter of Harwood Casson (1851-1889), general practitioner. David and his elder brothers all attended The Leas; David went on to Oundle, his brothers had both gone as scholars to Liverpool College.
Due to arthritis, David was found unfit for military service, and spent most of WW2 with Marconi. After the war, he joined the teaching staff at The Leas, married, and started a family.
He taught at The Leas for only a couple of years, before being attracted away to Hampshire to join Maurice Wright, who had started his own prep-school: Marsh Court, Stockbridge.
David seems to have been popular at The Leas, perhaps partly because of his restoration of the 35mm carbon-arc projector in the projection-booth at the back of the theatre. At Marsh Court too he took charge of a projector (16mm), and won similar kudos.