A landmark in national life has just been passed. For the first time in recorded history, those declaring themselves to have no religion have exceeded the number of Christians in Britain. Some 44 per cent of us regard ourselves as Christian, 8 per cent follow another religion and 48 per cent follow none. The decline of Christianity is perhaps the biggest single change in Britain over the past century. For some time, it has been a stretch to describe Britain as a Christian country. We can more accurately be described now as a secular nation with fading Christian institutions.

There is nothing new in the decline of the church, but until recently it had been a slow decline. For many decades it was possible to argue that while Christians were eschewing organised religion, they at least still regarded themselves as having some sort of spirit-ual life which related to the teachings of Jesus. Children were asked for their Christian name; conversations ended with ‘God bless’. Such phrases are now slipping out of our vocabulary — to wear a cross as jewellery is seen as making a semi-political statement. Christians are finding out what it’s like to live as a minority.

Just 15 years ago, almost three quarters of Britons still regarded themselves as Christians. If this silent majority of private, non-churchgoing believers really did exist, it has undergone a precipitous decline. Five years ago, the number of people professing no religion was only 25 per cent.

[datawrapper chart="http://static.spectator.co.uk/CBbHg/index.html"]

Remarkably, the overall decline of religion in Britain has coincided with the arrival of three million migrants who tend to have more religious belief than British Christians. In particular, the visual impact of Islam, most obviously expressed in the proposal for a 9,000-capacity ‘super-mosque’ in east London that was rejected by planners last year, might give the impression that migration has brought a religious revival to Britain. Yet neither the growth of British Islam nor the huge influx of Christian immigrants from Africa and Eastern Europe has spurred a revival in public Christianity.

It is possible that the rise of Islamism has made casual believers less inclined to ally themselves with any kind of organised faith. Say ‘religious’ to many Britons and the next word that pops into their heads is ‘extremist’, or perhaps ‘bigot’ or ‘homophobe’. To the growing population of secularists, religion has become something to be treated with suspicion. Politicians who are religious find their faith used against them. Iain Duncan Smith’s Department of Work and Pensions was known by his critics as the Department of Worship and Prayer, the joke being that his reforms were inspired by a desire to save lives rather than money. In government, to be a Christian can be seen as a personal failing. The ambitious minister keeps his or her faith under wraps. It is unthinkable now that a Prime Minister would do as Mrs Thatcher did on arrival in Downing Street 37 years ago, and quote St Francis of Assisi. All Cameron has dared to say, quoting Boris Johnson, is that his faith comes and goes like the reception of Magic FM in the Chilterns.

The eclipsing of our national religion has deep implications for those who do retain faith, especially those who wish to pass it on to their children. They must now face the reality that they, no less than Muslims, Jews and Hindus, face being treated as oddballs.

As for the church itself, it is no use pretending there is a Christian majority whose non-attendance at church is just down to laziness. If church leaders wish to keep their buildings open, they will have to start from the beginning — with missionary work to recruit parishioners in a now-sceptical country.

Inevitably, the question of what is to be done about our national Christian institutions will arise. Is it appropriate that we are still invited to swear on the Bible in court? (Many new MPs routinely refuse to do this in the Commons.) Is it right that the Lords Spiritual should still have a role in the Upper House, or that church and state should have any formal connection at all? The British regard for tradition will see that such roles are preserved, but for nostalgic reasons. The aesthetics of Christianity — the architecture, the choral singing and so on — still pull in crowds, even if little of the liturgy is inwardly digested.

Christians, for their part, should not automatically associate a decline in religiosity with a rise in immorality. On the contrary, Britons are midway through an extraordinary period of social repair: a decline in teenage pregnancies, divorce and drug abuse, and a rise in civic-mindedness.

We cannot discount the possibility of a Christian revival; the Christian faith specialises in defying the odds. But it seems more likely that Britain will continue to muddle along as a post-Christian country with quaint customs that derive from its history as a deeply religious country. Some will find this sad, others as a sign of progress, but the greater majority will view it with indifference.