Boris Johnson’s chances of becoming the next Mayor of London have lengthened on Betfair after he told a group gathered by the homeless charity Shelter how he lived in a big house worth “shedloads of money”.

Johnson is now 8-13 on Betfair to win May’s contest, having been as short as 2-5 earlier this week.

Ken Livingstone, meanwhile, described more modestly how he had bought his home for £160,000 in 1989.  As a result the Betfair odds of a prolonged stay in City Hall for the incumbent have shortened to 7-4, in from 11-5 yesterday.

Betfair users were first to respond to the news – with odds at traditional bookmakers remaining the same – as customers reacted quickly in order to get the best odds possible.

Betfair spokesman Mike Robb commented: “The ability Boris has for sticking his foot in his mouth has been kept under control recently and this is the first time we’ve seen him slip up in this election.  Until now it has been a case of Ken doing Boris’s hard work for him, but the race will become much closer if the Tory continues to provide Ken and the voting public with this kind of ammunition.  An ICM poll today put Johnson just 1% ahead, so who knows what is going to happen?”

To be Next Mayor of London – Betfair bet: 8-13 Boris Johnson, 7-4 Ken Livingstone, 74-1 Brian Paddick, 279-1 Any Other Candidate