To capture the full absurdity of the letter from 55 progressive thinkers in today’s Daily Telegraph, one would require the pen of the late Michael Wharton. He had an infallible ear for the self-importance of such people. Glancing down the list of signatories, with their faintly preposterous names, one cannot help suspecting quite a few of them do not actually exist, but were created by Wharton for his Peter Simple column in the Telegraph. It would be a simple enough matter for these thinkers to band together and draw up a rudimentary manifesto, after a period of wandering, disorientated, in the Court and Social page, where the less scrupulous of them have no doubt taken the chance to accumulate the honours to which they consider themselves so richly entitled.

These malcontents have now taken advantage of the Christian feast of Easter to mount a surprise assault on the Letters page, whose bank-holiday staff were in no position to resist such an unexpected thrust from a force whose natural home, insofar as such a thing exists, is in what used to be known as the Manchester Guardian.

Their letter begins with the words, “We respect the Prime Minister’s right to his religious beliefs”. How gracious of these thinkers to allow David Cameron to think what he wishes about religion. The implication is that they are being generous to allow the wretched little man even that much freedom.

For they go on to object with great earnestness to his description of this country as “Christian”. In order to rebut his claim, they assert that Britain is only Christian “in the narrow constitutional sense”. They manage to ignore not only our Christian history, but the presence of Christian places of worship in every city, town and even village in the land. In not a few of our most impoverished districts, the priest is the only member of the educated middle class who does not retreat at the end of the working day to some more salubrious spot.

It is generally considered a good thing for our politicians to reveal something of what makes them tick. Even the signatories of this letter would probably agree with that statement. But now that Cameron has described, in the most tactful language he can find, the Christian springs of his conduct, and his rather hazy idea of this as a Christian country, he is found to have committed an unpardonable provocation.

As I attempt to explain in a piece in today’s Financial Times, Cameron’s Anglicanism actually holds the key to his politics. It is highly desirable that he should tell us something about his religion. How ridiculous of the letter-writers to claim he is “constantly” going on about it, and to accuse him of thereby fostering “alienation and division”. This country’s gradual extension of toleration to different denominations of Christian has made it more natural for us than for some other societies to extend toleration to Jews, Muslims and members of other faiths. France is a great nation, but its history should perhaps make one hesitate before insisting that arrogant secularism can avoid fostering alienation and division.

The unselfconscious arrogance of these letter-writers is one of their most striking characteristics. They believe themselves to be liberals, yet cannot brook any defiance of their own views. They set out to insult a prominent Christian, and overlook millions of unknown Christians.

Lord Melbourne once remarked, on hearing an Evangelical Sermon: “Things have come to a pretty pass when religion is allowed to invade the sphere of private life.” But for these letter-writers, the real scandal is that Christianity should continue to play a natural and uncontentious role in public life. They wish to narrow and diminish a tradition of behaviour, and of politics, which to this day is more Christian than they are willing or able to understand. One of the virtues of their letter is that it may help to make this latent Christianity more visible.