In 1979, when the Conservatives were returned to power under Margaret Thatcher, Sir Malcolm was appointed a Parliamentary under-secretary of state, at first in the Scottish Office and then, at the time of the Falklands War, he was transferred to the Foreign and Commonwealth Office, being promoted to minister of state in 1983.
He became a member of the Cabinet in 1986 as secretary of state for Scotland. In 1990 he became secretary of state for transport and in 1992 secretary of state for defence. From 1995-97 he was foreign secretary.
He was one of only four ministers to serve throughout the whole premierships of both Margaret Thatcher and John Major for eighteen years. This represents the longest uninterrupted ministerial service in the United Kingdom since Lord Palmerston in the early nineteenth century.
In 1997 he was knighted in recognition of his public service. He has served on the Court of Edinburgh University and has been an honorary colonel in the Reserve Forces. He is a member of the Queen’s Bodyguard, the Royal Company of Archers.