Guido did hint at this back in June when there were febrile rumours of injunctions, newspapers camped on doorsteps and even a bastard baby Boris.

The Mirror says there is no suggestion of an affair and then suggests exactly that, while the high-minded Guardian uses the excuse of Helen McIntyre’s unannounced involvement in his “Olympian Erection” to justify its coverage, quoting a Boris spokesman saying that it was the Mayor’s “enthusiasm for private philanthropy” that meant her appointment as a fundraiser on the project had never been publicly announced. Boris clearly likes a bit of “private philanthropy” on the side.

Over at The Evening Standard they explain how this simple ‘friendship’ drove McIntyre apart from her billionaire partner Pierre Rolin. She later reported Rolin for harassment – but not before she’d found time to shag date William Cash, son of Tory MP Bill. So she clearly has a penchant for Tories.

Currently the City Hall game-plan is to say nothing, a plan that has worked up until this morning, given that the rumours have been swirling around since before the general election. Nobody is likely to confess to having had an affair and it is hard to see Ken making an issue of it given the five kids he has fathered by three different women (impressively managing to get two women simultaneously pregnant). Neither is Lembit likely to raise sexual athletics as an issue. The London mayoral contest is not going to be lacking for virility…

It could still get a little embarrassing for Boris, Charles Moore cracks this joke about Boris in speeches “I told Boris I don’t care what he does in his private life and he told me ‘Nor do I’ “.  There is also an attractive American woman who escaped to New York and entertains friends in Manhattan with anecdotes about her pursuit by Boris. His chat up line to her she says was, “I limit myself to one mistress per annum. How would you like to be Miss 2009?” Guido reckons Boris is nevertheless electorally bullet-proof, since it won’t be news to the voters that he is a serial shagger…