Rory Stewart is 3.3512/5 to be the next Mayor of London after he resigned from the Conservative Party and announced he would stand as an independent in next May's election.
Stewart, who set out his reasons for quitting the Tories and standing for Mayor of London in a video, is second favourite behind the incumbent Sadiq Khan 1.738/11.
Uphill struggle in a Labour city?
Khan came to power in the capital with an emphatic victory in May 2016. He was expected to win a second term against the Tory candidate Shaun Bailey 13.5 and the Lib Dems' Siobhan Benita 11.010/1.
Stewart, though, has ignited the contest by announcing his candidacy. He has been the MP for Penrith and Borders since 2010 but came to national prominence this summer with his run for the Conservative Party leadership. He walked the country, speaking to the public and arguing that Britain needed to avoid a disastrous no deal Brexit.
He faces an uphill battle to win the London mayoralty. Khan is not necessarily the most popular mayor and, with critics claiming he has failed to tackle knife crime in the capital, Stewart will surely draw on his time as justice secretary. But support for Labour has grown in the capital this decade. At general elections, there has been a swing to Labour of 9.7 percentage points since 2005.
But that didn't stop a certain other Eton-educated Tory, who had a way with words and liberal attitudes, winning the mayoralty in 2008 and '12. Boris Johnson, though, was up against Ken Livingstone, an unpredictable veteran who looked increasingly out of touch. Khan will be a stronger opponent for Stewart.
"Plenty of backing for Stewart"
There is no doubt, though, that Stewart's candidacy will make the 2020 race for city hall more interesting. If he wins, he will be a thorn in the side of the Tory government, if it's still in power by then.
Betfair Spokesperson Katie Baylis said: "After announcing his resignation from the Tories and his intention to run for London Mayor we've seen plenty of backing for Rory Stewart on the Betfair Exchange in the last couple of hours and he's now the clear second favourite behind Sadiq Khan who is odds-on. Shaun Bailey is a long shot despite his impassioned speech at this week's party conference."