Today’s vote in the House of Commons in support of gay marriage shows that sometimes history can move with breathtaking speed. Not very long ago the last Conservative Prime Minister, John Major, made front-page news because he agreed to meet the actor Ian McKellen in No 10. McKellen had recently come out as gay. The well-intentioned Major offered the actor little more than a cup of tea, but even this tiny, symbolic gesture of goodwill caused a stir.

Now a Conservative Prime Minister supports gay marriage and is acting to ensure the proposal becomes law. Some lives will be enhanced as a result, a wider signal will be conveyed about tolerance in a modern society, historians will note how speedily the change has happened in a country supposed to be instinctively conservative and the issue will have no lasting political impact whatsoever.

In one of the increasingly few differences between UK and US politics, social issues play little or no part determining the fate of parties here or their leaders. The Conservative party is split over gay marriage. There is intense anger among some MPs and activists. Some older Tory members may resign. The party will cope. Modern parties are much less dependent on high levels of membership than they used to be. Some Tory MPs are angry with Cameron. They were angry before gay marriage and will be angry for other reasons after it becomes law.

Cameron and George Osborne will be proved right in their calculation that in six months’ time the internal anger will subside. This is partly because the implementation of substantial one-off social reforms has a beginning, middle and end. The end will occur once the legislation is passed and gay marriages start to take place. For leaders of troubled parties the nightmarish political stories, the ones that can destroy them, are those with no obvious end. Europe, the economy and public service reform come into that category. Gay marriage does not.

Relax, Cameron

The Tory leadership can therefore be relatively relaxed about the headlines this week about division over gay marriage. This is a policy area that cannot sustain or fuel an insurrectionary fever. Cameron and Osborne’s motives in pursuing this are no doubt multi-layered, but that is the case with most decisions taken by any leadership. In an article last month, Osborne noted that the policy was popular in every region of the country. They seek association with a popular reform. Both must be aware of the chasm between their early tonally progressive messages and their agenda since the financial crash in 2008. Support for gay marriage has an echo of the early months of Cameron’s leadership. But beyond their clunky attempts to “modernise” they are acting out of conviction too. History will recognise their role in introducing a social change that will endure, unlike some of their other radical policies.

Gay marriage is part of an unstoppable sequence of social reforms that began with the lowering of the age of consent, the scrapping of Section 28 and the go-ahead for civil partnerships under the last Labour government. In each case most voters were on the side of change, an important part of the explanation as to why this particular sequence has reached a denouement so quickly.

But for the same reason the Conservative party will move on from the division over this issue, the leadership is unlikely to secure any electoral benefit from the change. Gay marriage will play no part in the next general election campaign, even subliminally. Labour’s Home Secretary, Roy Jenkins, introduced a series of historic social reforms in the late 1960s, reflecting and shaping the zeitgeist of that decade. Labour was removed from power in 1970 and Jenkins’ epoch-changing policies played little part in the campaign. Similarly Labour’s progressive social reforms after 1997 had little impact in subsequent elections.

Cheer

Forget about the narrow political implications and cheer the direction of travel. Section 28, which prohibited local authorities from “promoting homosexuality”, was still law until 2003, only 10 years ago. Cameron was one of those Conservatives who publicly and repeatedly attacked its abolition. According to the diaries of Lance Price, an adviser to Tony Blair, the Labour Prime Minister was nervy about the introduction of civil partnerships, in particular about the reaction of some right-wing newspapers. He still introduced them and like the smoking ban – another change of historic significance but with no impact on politics – the policy was implemented without explosive controversy.

The Tory split is triggered by a free vote where MPs can and should act according to their beliefs. It should be viewed in such a light. The outcome of the vote matters more. Soon if McKellen has a cup of tea at No 10 he can do so as a gay with the right to marry. Last time in his chat with Major he was pleading fruitlessly for the scrapping of Section 28. If only change could happen so quickly in the economy and public services, but in these areas there is no consensus between parties or within them as to what form the change should take. Social reform changes lives, arouses fleeting passions and is also, oddly, politically easier to bring about.