Lock was born at Herschel House, Cambridge, the youngest son of John Bascombe Lock (18 March 1849 – 8 September 1921) who was bursar of Gonville and Caius College, Cambridge,[3] and Emily née Baily.[4] His brother was Robert Heath Lock. Lock was a Scholar at Charterhouse School, and in 1912 was awarded a Major Scholarship at Gonville and Caius College,[5] where he was the only b* wrangler of 1917.[6] He took his BA in 1917, won a Smith's Prize in 1919, and became a fellow of Caius College in 1920.[4][5]
He was a Fellow of the Royal Aeronautical Society and the Physical Society.[9] He was a member of various committees of the Aeronautical Research Council.[5]
Lock married Lilian Mary née Gillman (1886/7–7 Oct 1966, aged 79) on 26 April 1924, at St Leonard's Church, Streatham.[10] They had two sons, Robert Christopher (Robin) Lock (14 Aug 1925–19 March 1992) and John Michael Lock (25 Oct 1926–2 March 2002),[4] who were both research students at Gonville & Caius.[5]