Its closest result was a 1.29% majority at the 1966 election which saw the start of the Second Wilson Ministry.

1885–1918: The Parishes of Hornsey (including South Hornsey) and Finchley (and the area included in the Parliamentary Boroughs of the City of London, Finsbury, and Islington for many wealthy voters this sub-provision gave a choice of which seat to vote for).

[clarification needed] 1974–1983: The London Borough of Haringey wards of Central Hornsey, Crouch End, Fortis Green, Highgate, Muswell Hill, South Hornsey, Stroud Green, and Turnpike.

McGarel-Hogg was elevated to the peerage, becoming Lord Magheramorne, causing a by-election.

The political parties had been making preparations for an election to take place and by the Autumn of 1939, the following candidates had been selected;