Every year, researchers from the British Social Attitudes survey ask a representative sample of British people whether they regard themselves as belonging to any particular religion and, if so, to which one? When the survey first asked these questions in 1985, 63% of the respondents answered that they were Christians, compared with 34% who said they had no religion (the rest belonged to non-Christian religions).

Today, a quarter of a century on, there has been a steady and remarkable turnaround. In the latest 2010 BSA report, published earlier this month, only 42% said they were Christians while 51% now say they have no religion. Admittedly, some other surveys – including the last census – have produced different findings on these issues, usually to the advantage of the religious option. There is also a margin of error in all such exercises. All the same, and particularly since the trends in opinion over time seem well set, it is hard not to feel that this latest finding marks a cultural watershed.

This Christmas, for perhaps the first time ever, Britain is a majority non-religious nation. Most of us have probably seen this moment coming, but it is a substantial event nonetheless. It is undoubtedly a development that would have astonished our ancestors who built a Britain on the basis that we were and would remain a predominantly Protestant people. The victory of secularism would have flabbergasted them almost as much as the pope appearing on the BBC with his Thought for the Day.

The change ought certainly to inspire some national reflection, though there is no need for national breast-beating. After all, in most eyes, the BSA survey finding simply underscores things that have already become obvious. Today, our three political parties are led by two open atheists, and a prime minister who admits his faith comes and goes, a development impossible to imagine in other parts of a world, in which the loss of religion is not a uniform trend. The Britain of 50 years ago, in which religion was a far larger part of the social fabric and the national way of life, is a country we have lost.

What is more striking about the survey is how quickly the change has come – just a generation. It is not that long since everything shut on Sundays, since a majority went regularly to church of some sort, since all schoolchildren knew and sang hymns and studied the Bible even if they did not believe in it, and since the idea that public figures could be anything other than observantly Christian would have seemed unthinkable. It would be hard to say, by most yardsticks, that those were better times. They were certainly different ones. The direction of change is likely to continue. We must all get used to it.

None of this is to dismiss the religious or to disparage its institutions, let alone to imply that Christmas is unimportant. For all its secular and commercial excess, Christmas remains a surprisingly serious season, accentuated this year by the bleak weather. But it is to say that sensitive adaptation to the predominantly non-religious era is required on all sides. In many respects, Britain is handling that task quite well. Our national evolution into a less religious society is not without its skids and bumps. If anything, though, it is being managed with greater dignity than our parallel evolution into a less politicised one.

It is no more the place of a newspaper to impose a religious test on its readers than it was right for the British state to impose such tests on its office-holders in the past. In some sense, the protection of respect becomes more important with Christianity's decline. When Anglicanism held unchallenged sway, after all, it was important to assert the rights of those who disagreed with it, whether as Catholics, nonconformists, non-Christians or as atheists. Today, as an era of non-religious ascendancy begins in Britain, the importance of tolerance towards the faiths is not diminishing but increasing.