[2][3] At the 1964 Rutherglen by-election, he only lost the Labour selection meeting fairly narrowly to Gregor Mackenzie, and he went on to take West Renfrewshire from the Conservatives at the general election later that year.
Buchan was also influential in changing the voting system[clarification needed] for the referendum on Scottish Home Rule in the late 1970s.
During Labour's 1981 deputy leadership election, he supported John Silkin, who stood representing the political centre of the party, on the first ballot and abstained on the second ballot after Silkin was eliminated and the contest came to Tony Benn on the left and Denis Healey on the right.
He was succeeded as MP for Paisley South by Gordon McMaster, also of the Labour Party.
He was married for 44 years (1946–1990) to Janey Buchan (née Kent), Labour Member of the European Parliament for Glasgow from 1979 to 1994.