On a turnout of 48%, the Labour Party held the seat.
Background
Labour had held the seat for 30 years, having won it at the 1950 general election. McMillan had been the MP for the seat since 1966.[1][2]
Candidates
This was the last parliamentary by-election in England, Scotland or Wales not contested by an official candidate of either the Liberal Party, the SDP, or their successor party the Liberal Democrats; until the 2008 Haltemprice and Howden by-election. The Social Democrat candidate had no connection to the SDP (which wasn't created until 1981) and achieved the lowest vote for any candidate in a Parliamentary election under universal suffrage, a record later surpassed by the five votes obtained by independent campaigner Bill Boaks in the Glasgow Hillhead by-election of March 1982.
While Labour won, the good performance of the SNP was described by The Glasgow Herald as the "surprise of the night" and the newspaper argued it marked their return "to the political stage" and that "both the major parties... were shaken" by the SNP's share of the vote.[1]