Boris Johnson has risked alienating the Conservative right by publicly backing the Government's plans to legalise full gay marriage.
In a short film made for the Out4Marriage campaign the Mayor of London said he was pleased that marriage rates are going up in London and that nobody should be denied the benefits.
But perhaps sensitive to the divide in his party over the issue, Mr Johnson backed the proposals without using the phrase "gay marriage" once. He also used most of the 38 second slot to plug his other achievements as Mayor – rather than espouse the cause of equality.
In the video he says: "One of the amazing things about London is that it's not only got a declining crime rate, declining murder rate, more theatres than New York, less rainfall than Rome but it's also one of the few places in the country where the rate of marriage is actually increasing and I see absolutely no reason why that happy state should be denied to anybody in our country. And that's why I'm supporting the Out4Marriage campaign."
Support from Mr Johnson, who is arguably the most electorally successful Conservative in the country, will be welcome to the Prime Min-ister, who is facing a bitter party split on the issue and a possible revolt at the autumn party conference.
Benjamin Cohen, of Out4Marriage, said he was pleased the Mayor was supporting them. "Boris Johnson like many has been on a journey when it comes to this issue and we welcome his support for Out4Marriage."
Mr Cameron pledged to enact gay marriage two years ago and a formal consultation is under way. However, it was not mentioned in the Queen's Speech, which raised fears among campaigners that he was getting cold feet. Downing Street denies this and insists legislation will be forthcoming before the next election.