Lord Glenarthur served in the government of Margaret Thatcher in the House of Lords, and in 1982 became a Lord-in-waiting (Government Whip) and became Parliamentary Under Secretary of State at the Department of Health and Social Security (DHSS) in 1983. He then moved to the Home Office before being promoted to Minister of State for Scotland in 1986. His last ministerial appointment was as Minister of State for Foreign and Commonwealth Affairs from 1987 to 1989. Amongst his particular responsibilities were Hong Kong and the United Kingdom's relationship with China.