This chart sums up an extraordinary week of bloodletting and intrigue. It shows the betting on Gordon Brown leaving office before the end of June. At the peak of the leadership crisis on Thursday night, after James Purnell resigned, the chance of Brown resigning stood at 65 per cent. It is now back down to around 10 per cent.

Remember this chart is from Betfair, an online betting exchange which works a bit like a market. The odds reflect the price the punters are willing to offer each other, rather than the views of one bookie. Read more