In a withering aside, Randall added that he knew he was “going to be on the wrong side” because those who supported same-sex marriage were “some of the nicest people I came across, something that couldn’t be said about those opposing”.

Randall ended by reflecting that in hindsight he wished he had spoken to a fellow MP before the vote who "said to me that it was something that wouldn’t affect him at all but would give great happiness to many people”. And he concluded: “Three years on I can honestly say I was wrong and I am sorry not to have been able to see it at the time.”

Sir John Randall's apology in full:

There are not many things that I regret about my time as an MP but almost as soon as I voted against same sex marriage I knew I had made a mistake. Of course I recognised that it was going to go pass anyway so my vote was not crucial and I was wavering. I excused myself with my children with the excuse that I would have voted for it had civil partnerships been allowed for heterosexuaI couples and I still think that should be actively considered but in the end as a Government Whip I was a teller and therefore technically didn’t vote one way or the other. That was not courageous.

I think I was just not ready for this step, conflicted between many of my age group and those of the younger generation whose views I wanted to understand. Ultimately I think I knew that I was going to be on the wrong side as those who wanted to me to vote for were some of the nicest people I came across, something that couldn’t be said about those opposing. With hindsight I wish I had spoken to a very good friend and colleague before the vote. He might easily have been expected to oppose the move to same sex marriage but he said to me that it was something that wouldn’t affect him at all but would give great happiness to many people. That is an argument that I find it difficult to find fault with.

So three years on I can honestly say, I was wrong and I am sorry not to have been able to see it at the time.

The apology arose after BuzzFeed News emailed every MP and former MP (apart from those whose email addresses are no longer publicly available) who voted against same-sex marriage to ask how, three years since the first weddings, they felt now.

The issue proved highly contentious during its passageway through parliament, prompting fierce debates in the House of Commons in early 2013. David Cameron, then prime minister, championed the cause for marriage equality, much to the chagrin of large parts of his party.