New London mayor Sadiq Khan today triggered a Parliamentary by-election by resigning as the Labour MP for Tooting.
A spokesman confirmed the mayor was asking to be appointed to the Crown Steward and Bailiff of the Chiltern Hundreds - the formal mechanism for standing down.
Labour said the by-election was likely to be held on June 9th or June 16h.
Mr Khan, who has represented the seat since 2005, had a majority of 2,842 in the general election in May 2015.
The mayor is following a tradition set by his predecessors. Ken Livingstone and Boris Johnson both resigned as MPs after being elected to City Hall.
Former Respect MP George Galloway told ITV News last month he planned to contest the Tooting seat.