But should you be making a 75/1 insurance bet on Paddick?

The chart, using betting prices expressed as implied probabilities, shows the dramatic changes there have been in the London Mayoral race betting over the past week.

Last Saturday the Labour incumbent, Ken Livingstone, was the marginal odds-on favourite with his Tory challenger, Boris Johnson, not far behind. Then the came the national general election polls showing a huge move to the Tories in the aftermath of the budget.

This was followed on Monday with the first Mayoral poll of March giving Johnson a seeming unassailable 12% lead and the following day we had a further national poll from ICM suggesting that the Tory lead was getting larger.

The main hope for Ken is that the latest mayoral poll was taken straight after the budget which clearly bombed with the public but which might be a temporary phenomenon.

Ken loyalists usually argue that the pollster, YouGov, has a history of understating their man’s support – a notion that is based on the Evening Standard’s selective use of data just before polling day in 2004. The survey itself and the numbers most directly comparable with this week’s poll got it almost exactly right. In February Labour published details of is own private MORI survey to counter the first YouGov poll showing Boris ahead. That’s not happened this month suggesting that the pollster is now in the same area as YouGov.

An issue for the betting now is whether the Lib Dem, Brian Paddick, could be in with a shout. A number of figures on the left such as the writer Nick Cohen are promoting a vote for Paddick as the only way of stopping the Tory. If this catches hold and there’s a big move to the Lib Dem in the next polls then the notion might gain some traction. If he came second on the first count, the argument goes, he would pick up the lion’s share of Ken’s second preferences. Even then I don’t think that Paddick can overhaul Johnson but I’ve covered my betting position with a £30 punt on the Lib Dem at 75/1.

I cannot recall a Tory or the Tories ever losing an election when within six weeks a poll has shown them enjoying such a margin. There might be a precedent but I am not aware of it.

Latest mayoral betting prices are here.

Mike Smithson