As Starmer quits, collapse of U.K.’s mainstay parties mirrors global trend

LONDON — Announcing his resignation on Monday, U.K. Prime Minister Keir Starmer appeared in a uniquely British tableau: the small lectern, the glossy black door, the brass “No. 10” gleaming over his shoulder. Starmer was the sixth occupant of Downing Street to quit under pressure in the last decade.