Boris Johnson used to be king of the capital. As a politician who presented himself as metropolitan and socially liberal, he gave the Conservatives their first control of London-wide government for 30 years by winning the mayoralty in 2008.
But now the party is facing one of its toughest electoral tests in the city, and the prime minister risks insurrection from his own backbenchers if the Partygate investigations threaten to hit them at the ballot box too.
