After inheriting his father's title in 1975 Boyd took his seat in the House of Lords, eventually joining the Social Democratic Party (SDP), which according to his obituary in The Times "suited his political instincts admirably"."Obituaries: Lord Kilmarnock", The Times, 24 March 2009, p. 55. He served as the party's chief whip in the Lords from 1983 to 1986. He was the deputy leader of the SDP Peers from 1986 to 1987, and served as the chairman of the All-Party Parliamentary Group on Aids from 1987 to 1996. A loyal follower of David Owen, in 1988 he joined him in rejecting the SDP's merger with the Liberals by forming the breakaway 'continuing' SDP instead. Reportedly "saddened" by the original party's demise, he remained associated with the Owenite rump party and its even smaller successor until 1992, thereafter sitting in the Lords as a crossbencher. Along with many other anti-merger Social Democrats, including Owen himself, Boyd was also instrumental in establishing the Social Market Foundation think tank, and was appointed its first executive director in 1989.David Owen, Time to Declare (London: Penguin, 1992), p. 802.
