The Conservatives won 1,922 votes in the Holborn and St Pancras by-election on 8 October 2026, which the Guardian put at 7.1%, above 5%; BBC News gave the vote count; Camden's full results page could not be read because it blocks automated visits.
The Conservative share market resolves YES if the Conservative candidate takes under 5.0% of the votes cast in the declared result, the line at which a candidate loses the deposit, and NO at exactly 5.0% or above. Camden's declaration settles it, with the Electoral Commission's certified figures governing any correction and the BBC and the Guardian as the backup record.
We looked at UK byelections since 2012 where the leader of a national party stood in person, and checked whether more than 40% of voters turned out. We found six. Four passed 40%, and none passed 51%.