Boris Johnson's call for all school pupils to do two hours of sport  a day, following the news that the government has scrapped  the relevant target, is yet another example of him using his platform as Mayor of London to make a national intervention.
Here's what he told a press conference earlier today:
The government totally understands people's appetite for this, they can see the benefits of sport and what it does for young people.
They understand very, very clearly the social and economic advantages.
I would like to see, frankly, the kind of regime I used to enjoy - compulsory two hours' sport every day.
I've no doubt that is the sort of thing that would be wonderful for kids across this country.
It is of profound importance for the happiness and success of this country that we have more sport in schools.
David Cameron has defended the decision to abolish the target on the grounds that "if you just simply sit there in Whitehall and set a target but don't actually do anything to help schools meet it, you are not really solving the problem". He added: "By just saying 'Look, I want you to do this many hours a week' some schools think 'Right, as I've hit that minimum requirement, I've ticked the box and I can give up."
Yet, as ever, Boris has not missed an opportunity to kick Cameron while he's down. As Mayor of London he enjoys the luxury of being able to comment on national affairs with little fear of consequences, while the PM is constrained by the coalition, his own MPs and the government's deficit reduction plan. If today's intervention is a sign of things to come, the next three years could be very uncomfortable for Cameron.