  Alan Mathison Turing was born in London, 23 June 1912, to upper-middle-class British parents. His schooling was of a traditional kind, dominated by the British imperial system, but from earliest life his fascination with the scientific impulse—expressed by him as finding the ‘commonest in nature’—found him at odds with authority. His scepticism, and disrespect for worldly values, were never tamed and became ever more confidently eccentric. His moody humour swung between gloom and vivacity. His life was also notable as that of a gay man with strong emotions and a growing insistence on his identity.