The guests at the state dinner for British Prime Minister David Cameron last month queued up in the East Room for the receiving line to meet him and President Obama in the Blue Room. It is during that time that they think of what to say to the president. For me, it was greetings from my mother, Aunt Lillian and Giuseppe.But another guest used that opportunity to deliver a message to liberal Obama by way of conservative Cameron.

“Mr. Prime Minister, thank you for all that you’re doing for marriage equality in Great Britain,” the guest said to Cameron, who was standing to Obama’s right, literally and figuratively. With a gesture towards the president, Cameron replied, “It takes a conservative to convince a liberal about gay marriage.”

As The Post’s Anthony Faiola reported last week, Cameron is blazing new territory by proactively pushing for marriage equality in a nation that already offers civil partnerships, which grants the same rights to same-sex couples that heterosexual married couples enjoy. And by doing so, he’s redefining what it means to be a conservative in the United Kingdom.

“I don’t support gay marriage despite being a Conservative,” Cameron said in a recent landmark speech on the issue. “I support gay marriage because I am a Conservative.”

Faiola notes that Cameron “gradually evolved” on the issue of same-sex marriage beginning in 2005. Obama continues to “evolve” on the issue, much to the consternation of many. But there’s no doubt in my mind that the president’s evolution is proceeding apace and in the right direction. The Department of Justice no longer defends the so-called Defense of Marriage Act in court. Obama lauded the New York state legislature’s historic passage of a marriage equality bill last year. And he has spoken out against efforts in New Hampshire, North Carolina, Maine and Washington to deny or take away rights from same-sex couples.

The one thing Obama hasn’t done is say flatly, “I support gay marriage.”

If actions speak louder than words, then there should be no doubt where Obama stands on marriage equality. But for many, until the words of the president of the United States match his actions, he’ll remain on the wrong side of history and to the right of Cameron.