Watch: Keir Starmer speaks in Selby and Ainsty after Labour’s Keir Mather wins seat

Watch as Sir Keir Starmer speaks in Selby and Ainsty on Friday, 21 July, after Labour won the seat in Thursday's by election.

Keir Mather will become the youngest MP in the Commons at 25 years old after overturning a 20,137 majority in the North Yorkshire constituency.

Labour said Mr Mather's 4,161 majority in the seat was the highest majority the party had ever overturned in a by-election; the 23.7 per cent swing from Conservative is the second largest swing managed by Labour at a by election since 1945.

The opposition party’s victory came as the Liberal Democrats took Somerset and Frome.

Rishi Sunak was spared being the first prime minister since 1968 to lose three by-elections on the same day as Labour failed to secure victory in Boris Johnson’s former seat of Uxbridge and South Ruislip.