Labour’s victory at Selby and Ainsty has made history: it is the largest Conservative majority (20,137) overturned by the party at a by-election since 1945. The previous record was set at the Mid Staffordshire by-election in March 1990, when Labour overturned a Tory majority of 14,654. To win the seat, Labour needed a swing in the share of the vote of 17.9 percentage points: the equivalent of a net change of 18 in every 100 people who voted Conservative at the 2019 general election switching sides. They managed a swing of 23.7 points: the largest achieved by Labour at by-election since it won Dudley West from the Tories in December 1994 (29.1 points) and the second largest swing managed by Labour at a by-election since 1945. The Conservative share of the vote in Selby dropped sharply from 60% at the 2019 general election to 34%, while Labour’s share rose from 25% to 46%. The winner, 25-year-old Keir Mather, will become the youngest MP in the House of Commons. Click here to subscribe to The Independent: https://bit.ly/Subscribe-to-Independent About The Independent: Making Change Happen. The Independent is the world’s most free-thinking newsbrand, providing global news, commentary and analysis for the independently-minded. Connect with The Independent: Check out our full video catalog: null Videos, daily editorial and more: http://www.theindy.com/ Click here to get the best of The Independent daily: https://www.independent.co.uk/newsletters Like The Independent on Facebook: https://www.fb.com/TheIndependentOnline Follow The Independent on Twitter: https://twitter.com/Independent Follow The Independent on Instagram: https://www.instagram.com/the.independent Download the iOS & Android app: https://www.independent.co.uk/subscribe/app Help to support truly independent journalism. Every dollar you contribute will directly fund additional special reports and investigations from a free-thinking, award-winning newsroom you can trust - https://www.independent.co.uk/donations Subscribe to Independent Premium for exclusive content & live events: https://bit.ly/2MiOONB