He was elected
MP for
Colchester in
a 1961 by-election. A strong supporter of the modernising Conservatism championed by
Edward Heath, Buck served as the Under-Secretary for Defence from 1972 to 1974 with responsibility for the
Royal Navy, but his fortunes declined when Heath lost the election in 1974, and he managed the unsuccessful leadership campaign for his old friend Geoffrey Howe. Buck then lost his place on the executive of the
1922 Committee, although he later regained it. Nevertheless, he remained a perceptive observer of defence policy, opposing the closure of Colchester's military hospital and other cuts. He was also chairman of the Parliamentary Ombudsman Committee. He was held in high regard by his constituency party and continued to serve as the MP for Colchester until 1983 when he became MP for
Colchester North after boundary changes. He retired from parliament in 1992. ==Marriages==