London's new attack dog

Ken's rolling out the big guns in his fight with Boris. Well, the small Catholic guns, anyway. Here comes Ruth Kelly to stick the knife into BoJo's bus estimates:

"Boris Johnson's transport policy is in tatters given this extraordinary underestimate of the cost of his bus policy by £100m a year," Kelly said. "Boris Johnson's got it wrong and it is time for him to come clean."

Ken's strategy's now pretty clear - portray BoJo as a bumbling fool who can't add up and shouldn't be left in charge of a Hornby trainset, let alone CrossRail. Whether that's more powerful than BoJo's line - that Livingstone's regime is a mess of corruption and cronyism - remains to be seen.