Spirituality is usually relegated to the sidelines in British politics. But with Tony Blair faith is back in the game - where, on closer examination, it has been for more than a few post-war British Prime Ministers

When in April Tony Blair delivered a speech about his faith and politics in Westminster Cathedral it was treated by the serious papers either as an add-on to the political story of the day or worthy of the equivalent of a parliamentary sketch. Only The Tablet produced a serious account of what the former Prime Minister actually said.

In similar vein, Howard Brenton's play Never So Good, about the 1950s and 1960s Prime Minister Harold Macmillan, and currently playing to good-sized audiences at the National Theatre, is tone deaf to Macmillan's Anglo-Catholicism, which was central to his being. Brenton's portrait of Ronald Knox about "to Pope" - as they called it during the Great War - depicting him as a crude, insensitive and repellent hearty, is a parody. It bears no relationship to the gentle sensitivity, wit and spirituality of Knox that captivated so many, Macmillan included.

Religion nowadays can only be guaranteed a place in the newspaper sun if it is laced with sexual scandal and/or personality clashes. There is a real danger that the religious and religious-related strand of social and national life will become increasingly written out of contemporary histories by scholars who are now tone deaf to it.

Indeed an examination of the spiritual lives of British prime ministers since 1945 provides a test case for assessing the difficulties historians have faced in recent times in calibrating religiosity or spirituality.

I will begin with Clem Attlee - my one political hero. He presided over a pair of Labour governments between 1945 and 1951 for most of whose members Methodism had been a more formative influence than Marx. However, Attlee himself, despite attending Haileybury Imperial Service College, a school suffused with Anglicanism, seems to have been entirely untouched by organised religion. In an interview with his official biographer, Kenneth Harris, he displayed his gift of terse, staccato riposte to almost hilarious effect:

Harris: Was it Christianity that took you into politics?

Attlee: Social conscience, I would say. Inherited it. My parents were very much that way.

Harris: But your parents were actually professing Christians, weren't they?

Attlee: Yes. And my brothers and sisters.

Harris: But you weren't?

Attlee: No. I'm one of those people who are incapable of religious experience.

Ken Harris persisted on the Christian theme:

Harris: Do you mean you have no feeling about Christianity, or that you have no feeling about God, Christ and life after death?

Attlee: Believe in the ethics of Christianity. Can't believe the mumbo-jumbo.

Harris: Would you say you are an agnostic?

Attlee: I don't know.

Harris: Is there an afterlife, do you think?

Attlee: Possibly.

How many people could tell you about Churchill and religion, even though more biographical ink has been spilt on him than any British prime minister in history? Churchill, like his nineteenth-century predecessor in Downing Street Lord Melbourne, gave the impression of supporting the Church of England from the outside as a flying buttress does a cathedral. However, he was not a believer. "I believe that death is the end," he told his friend Violet Bonham Carter.

What about Churchill's successor, Anthony Eden? He had a spiritual side certainly, as his biographer, Richard Thorpe, noted: "Awakening spiritual feelings came through his pantheistic love of nature, not organised religion. Although his mother was a devout Anglican, his father was self-consciously atheistic, and Eden inclined to the views of his father. Religion was never a powerful element in his life." His second wife, Clarissa Churchill, whom he married in 1952, was brought up a Catholic. An old friend, Evelyn Waugh, was very critical of her marrying a divorcé. Her cousin, Randolph Churchill, told Waugh that as he was neither a cardinal archbishop nor the editor of The Tablet so he should mind his own business.

So, the first 10 years after the war produced the following score in 10 Downing Street - Atheists and Agnostics United 3: Christians 0.

A pronounced comeback was imminent - thanks to Colonel Nasser and the Suez crisis of 1956 which, with worsening ill heath, brought Eden down in January 1957. For Eden was succeeded by Harold Macmillan, who late in life admitted it was a quirk of history that he had not become a monsignor and his friend, Ronald Knox, Prime Minister.

Macmillan didn't "Pope" and the relationship with Knox fell away. But it had one final and very poignant reprise during Macmillan's first few months as Prime Minister. In the spring of 1957, Knox was dying of liver cancer. He managed to get to Oxford from Somerset to deliver the Romanes lecture on 11 June 1957 to a packed Sheldonian. Then he travelled on to London to stay with Macmillan in 10 Downing Street and to be examined by the Prime Minister's doctor, who confirmed the diagnosis and that he did not have long to live. Macmillan drove with Knox to Paddington in the prime ministerial limousine. Macmillan saw him on to the train. "I hope you will have a good journey," said Macmillan.

"It will be a very long one," said Knox.

"But Ronnie you are very well prepared for it," replied the Prime Minister.

Those were their last words together.

Though Macmillan did not make a public fetish of his religion, "he remained to the end", wrote his official biographer, Alistair Horne, "a dedicated Anglo-Catholic, a church-going believer who took the New Testament with him to the trenches, and - as Prime Minister - showed more interest in church matters and appointments than perhaps any other incumbent since Gladstone."

Macmillan once said: "Whatever your views happen to be about practical theology, I don't think a nation can live without religion ... if you don't pray every night, and if you don't believe in God, and if you don't think you can serve God eventually, you can't solve all these problems and you can't even survive them ... when you gave up religion, you give up any kind of idealism."

Alec Douglas-Home, Macmillan's successor, whose premiership lasted but a year, was a Scottish Episcopalian who believed all his life. His faith came out strongly when I interviewed several of those who had worked with him for a BBC Radio 4 obituary, A Countryman in Downing Street. Sir Antony Acland, who served two spells as his Foreign Office private secretary, put it simply, declaring: "He had a Christian sense of right and wrong; and then what was right for his country."

Harold Wilson, who succeeded Douglas- Home in 1964, was brought up in the Yorkshire non-Conformist tradition as a Congregationalist and sustained his regular chapel-going as an undergraduate in pre-war Oxford. A contemporary of Wilson's at Jesus College, Eric Sharpe, reckoned there "was a deeply religious element in his make-up which influenced much of his political thinking in later years". Wilson said the same in an interview the year he became Prime Minister. His wife, Mary, in an interview with Wilson's biographer, Ben Pimlott, elaborated a little: "Religion was part of his tradition. He never questioned it, but he did not think much about wider religious questions. When he did, he believed that people should translate Christianity into good works."

But, as Pimlott noted, Wilson, the great political manipulator, suffered from not being taken at face value on this or anything else. "Labour colleagues," he wrote, "mainly atheistic or agnostic, viewed Harold's piety with cynicism. Set against his cat-like manoeuvrings at Westminster, it looked like humbug. Nevertheless, religious worship was part of the mould which formed him, his political outlook, and his idiom." I think we can place him as PM in the believing-but-not-belonging category.

So, 20 years after the end of the Second World War, we have a score draw on the Downing Street pitch - Atheists and Agnostics United 3: Christians 3.

In 1970, the Christians go ahead for the first time in the post-war period when Ted Heath enters Downing Street. His biographer, John Campbell, writing while Heath was still alive, said "his lifelong though unpublished fidelity to the Christian faith in which he was brought up has reflected and expressed itself principally through his love of music". After the war, Heath was briefly news editor of  Church Times, a fact in later life he did not bother to record in his Who's Who entry. At the time he described himself to friends as "a political fish in holy water". As leader of the Opposition and Prime Minister, Heath, as Campbell writes, "kept his Christian faith almost entirely hidden: he was photographed going to church far less often than Wilson, whose supposed Methodism sic was an important element of his Yorkshire non-Conformist image. Nevertheless in his deeply private way his belief remained one of the fixed decencies of Heath's life..." In private, too, as Prime Minister, he took great care over the 45 Anglican bishops he advised the Queen to appoint between June 1970 and February 1974, reckoning the choices were "often ... better than they would have been had they been left entirely to the Church with no involvement from Number 10".

Wilson returned to Number 10 for two years before being succeeded as Labour Prime Minister by Jim Callaghan in April 1976. Callaghan was brought up a Baptist in Portsmouth and was a Sunday-school teacher, which, I think, puts him in a class of his own among our 12 post-war premiers. After his father died young, the Callaghan family were in genuinely straitened circumstances and the London Road Baptists in Portsmouth "acted like an anchor" for them, Callaghan recalled in his memoirs.

When Callaghan moved to Maidstone as a young official in the Inland Revenue, he  appears to have lost his faith as politics took over. But he later wrote that even "in adult life I have never been able wholly to shake off a sense of guilt", though he did pray at difficult moments, especially during his testing three years as Chancellor of the Exchequer in the 1960s. And his Puritanism on matters of personal behaviour was evident during his premiership. Callaghan can just be placed, therefore, in the believing-but-not-belonging category.

"Uncertainty" is not a word one associates with Margaret Thatcher, who succeeded Callaghan in May 1979. She later wrote that her upbringing in Grantham "revolved around Methodism" and there was "never ... any danger" that she would lose her faith when she got to Oxford. "Methodism", she recalled, "provided me with an anchor of stability and, of course, contacts and friends who looked at the world as I did." As a girl, she envied the Catholics who went to Mass just opposite her home in Grantham. She recalled, "the Catholics seemed to have the most light-hearted time of all. I used to envy the young Catholic girls making their First Communion, dressed in white party dresses with bright ribbons. The Methodist style was much plainer, and if you wore a ribboned dress an older chapel-goer would shake his head and warn against ‘the first step to Rome'."

As Prime Minister, Mrs Thatcher had some set-tos with those who took a different interpretation of the economic and social meaning of the gospels to her own. The handbag swung at the Anglicans over Archbishop Runcie's sermon in St Paul's after the Falklands War in 1982 and over their report "Faith in the City", in 1985. And she enraged several members of the Church of Scotland in 1988 when she stormed up to Edinburgh, brandishing a speech she had largely written herself, and gave the impression of hammering conventional wisdoms about the social gospel. "How could we invest for the future," she cried, "or support the wonderful artists and craftsmen whose work also glorifies God, unless we had first worked hard and used our talents to create the necessary wealth?"

Of John Major's faith I had no idea until he published his memoirs in 1999. The Major household in south London talked neither of politics nor religion. But, wrote Major: "I always had a yen to take church more seriously than my parents did. That yen was largely unfulfilled. The Church appealed to me, but it never reached out to me. Though I was baptised into the Church of England I was never confirmed - and had I been in later life, when I had become a public figure, I worried that it would lead to comment about my motives. For my parents the Church was something rather quaint, an honoured but distant institution that other people attended but we did not - except, of course, for fetes and jumble sales. Chance and circumstance left me a believer at a distance; but a believer nonetheless." Another for our believer-but-not-belonger category.

Tony Blair's religious journey from Canterbury to Rome is too recent and too well known for me to need to map it out. Gordon Brown, as he frequently reminds us, is shot through with the values of the Manse. But in fact he is only an occasional - not a regular - attender at Church of Scotland services. Another believer-but-not-belonger, I suspect.

So, our final score is - Atheists and Agnostics United 3: Christians 9. Quite an interesting tally given the rise of secular society in Britain. And the unbelieving trio were all in Downing Street in the early post-war years before church attendances began to fall apace. Even though in the past I have expended a cataract of ink writing about post-war premiers, only recently have I thought about their spiritual lives in such detail.

The danger for future historians may be an inclination not even to look for belief, especially of the non-belonging kind. They may simply not understand in the British context (home-grown jihadism apart) the enduring salience for good and occasionally ill of at least part of what the great social anthropologist, Ernest Gellner, meant when he wrote in 1994 that "what makes humans human is religion", which in its turn "makes society possible twice over: by enabling people to communicate, and by engendering those shared compulsions, those inhibitions, which make social and moral order possible".