The mayor is at odds with the Conservative party again - this time over immigration. The Tories have gone against Labour and Liberal Democrat proposals for an immigration amnesty, citing Italy and Spain as examples of why this policy could increase illegal immigration, while Boris has said the idea should be considered.
Boris's clashes with his own party are many and legion, only a few weeks ago he suggested that a youth service scheme touted by David Cameron as voluntary should be instead be compulsory. In March, Boris refused to back the Conservatives' plans for high speed rail links and who can forget Cameron's high profile nixing of the mayor's estuary airport?
The ongoing differences of opinion - we hesitate to call it a feud, it's much too polite for that - have provided hours of entertainment for the media and bloggers alike. Boriswatch.com speculates that David Cameron sees the mayor as a threat and has a vested interest in keeping him out of Westminster, and Dave Hill notes that while Labour have offered support for Boris's pet project, Crossrail, the Conservatives haven't guaranteed it would go ahead if they were in power.
Do we forsee a Blair/Brown style in-house conflict in future years? Watch this space.