Swing when you’re winning

What are the biggest UK by-election swings?

— The 1983 Bermondsey by-election saw a 11,756 Labour majority turned into a 9,319 majority for the Liberal party – a result widely attributed to the Labour candidate, Peter Tatchell, coming out as gay during the campaign. The Labour party under Michael Foot was also extremely unpopular – and had its then biggest defeat in a general election four months later.