LONDON: Britain’s ruling Conservative party suffered a major upset in a by-election result announced Friday, losing a safe seat it had held for nearly 50 years.

Prime Minister Boris Johnson’s party lost in the contest to elect an MP for Chesham and Amersham — prosperous commuter towns in Buckinghamshire, northwest of London. The centrist Liberal Democrat candidate, Sarah Green, won more than 56 percent in a constituency that had been held by the Tories since it was set up in its current form in 1974.

The Times newspaper said the defeat raised questions over the Conservative strategy of focusing efforts on seizing seats from the main opposition Labour party, rather than on defending traditional Tory seats, known as the “Blue Wall” due to the party’s logo colour. Johnson’s party in May won a by-election in the traditional Labour-voting Hartlepool, adding another parliamentary seat in northeast England to those they secured in the last general election in December 2019.