Prime Minister Malcolm Turnbull made a surprise appearance at the Sydney launch of the Liberals and Nationals for YES campaign.

Previously the PM had said he would most likely be too busy to take any role in the campaign despite being a longtime supporter of marriage equality, and while he didn’t make it to a nearby rally that attracted record breaking crowds, he did make it to a Liberal and National supporters event.

Speaking to supporters at the Australian Museum, Turnbull said the issue was fundamentally about fairness.

The Prime Minister listed the many English-speaking countries around the world that have already legalised same-sex marriage.

“This change has already happened around the world,” he said.

“Now, in any one of those nations has the sky fallen in? Has life as we know it ground to a halt? Has traditional marriage been undermined? And the answer is plainly no.”

Turnbull said everyone was entitled to have a view of the issue and have a say via a democratic process. Turnbull said that conservatives should look to former British Prime Minister David Cameron for inspiration.

“This is a unique moment in our history,” Turnbull said declaring his hope that the postal survey would deliver a YES result. The PM said if the YES campaign is successful the legislation would sail through parliament before Christmas.

The Liberal and Nationals for YES has attracted a number of of high profile conservative identities who have voiced their support for marriage equality. Among them writers Janet Albrechtsen and Greg Sheridan, former Howard government Ministers Helen Coonan and Amanda Vanstone, former Brisbane Lord Mayor Sallyanne Atkinson, alongside current politicians Dean Smith, Greg Hunt, Warren Entsch and George Brandis.

Listen to the PM’s speech.