hill-norton was swiftly propelled into the post of first sea lord and chief of the naval staff in july 1970 and then, having been promoted to admiral of the fleet on 12 march 1971, into the post of chief of the defence staff in april 1971 following the unexpected early retirement of sir michael le fanu due to ill health. in the latter role he gave the final commitment to project chevaline, the polaris missile improvement programme. he became chairman of the nato military committee in 1974, remaining in that post until his retirement in 1977.