The roof did not fall in (though Mr Silvester did blame Mr Cameron for some flooding in 2014). Indeed, same-sex marriage has proved remarkably popular. As of 2020, the most recent year for which there is data, more than 42,000 gay couples in England and Wales had tied the knot. (Scotland and Northern Ireland passed separate laws.) Polling in June found that more than three-quarters of Britons now support gay marriage, up from just over half in 2012. Just 14% are opposed.

The success of same-sex marriage legislation shows how political leaders can shape and accelerate deeper shifts in public opinion. Britons have long been becoming more liberal and less religious. The previous New Labour government had done much to sweep away repressive legislation. It ended Section 28, which prevented schools and local authorities from “promoting homosexuality” and introduced civil partnerships. Campaigners were pushing for more.

Nevertheless, Mr Cameron chose to confront his party on a subject many would rather have avoided. “I don’t support gay marriage despite being a Conservative. I support [it] because I’m a Conservative”, he told his party’s annual conference in 2011. The government proceeded carefully, conducting a consultation which elicited the largest ever response. Still, Conservative mps attempted wrecking amendments and 134 voted against the bill, which meant that Mr Cameron had to rely on opposition votes. But the law was changed, and attitudes changed with it. Gay marriages became not an abstract threat but something undertaken by friends, colleagues, neighbours. Almost half of Britons now say they know a married gay couple.

This change reveals some deeper shifts. Gordon Brown, Mr Cameron’s predecessor, opposed gay marriage in office because it was “intimately bound up with questions of religious freedom”. Many others across the House did, too. Few would now admit to such a view. Danny Kruger, a Conservative mp, told a recent conference on “national conservativism” that marriages between men and women were “the only possible basis for a safe and successful society”. But there appears little constituency for such a message in Britain now. Number 10 quickly shot down the remarks. Like most successful and enduring policies same-sex marriage has moved beyond contention. Though Britain was not the first to legalise it, 19 other countries have since given gay marriage their blessing.