The seat had become vacant when the constituency's Liberal Member of Parliament (MP), Frank Kingsley Griffith (23 December 1889 – 25 September 1962) vacated his seat on becoming a County Court Judge.
The election took place during the Second World War. Under an agreement between the Conservative, Labour and Liberal parties; who were participating in a wartime coalition, the party holding a seat would not be opposed by the other two at a by-election. Accordingly, the Liberal Party nominated a candidate, but no Labour or Conservative representative was put forward. As no one else was nominated, there was an unopposed return and no poll took place.
The Liberal Party candidate, supporting the coalition government, was Harcourt Johnstone (19 May 1895 – 1 March 1945).
Johnstone was elected unopposed as the constituency's MP at the by-election. He sat for the seat until he died. Johnstone had previously been MP for Willesden East 1923 – 1924 and South Shields 1931 – 1935.
