There was a by-election for Belfast West constituency on 29 November 1950.
It occurred after the winner at the 1950 UK general election, James Godfrey MacManaway, was disqualified as he was a priest.
Thomas Leslie Teevan, the Unionist candidate, narrowly beat Jack Beattie, a former MP for the constituency who was the candidate of the Irish Labour Party, by 913 votes. However Beattie beat Teevan at the 1951 general election.
References
Belfast West by-election, 1950 Wikipedia(Text) CC BY-SA