Father Michael Seed may be, according to his great friend Ann Widdecombe, whom he received into the Catholic Church, "the missionary to celebrities", but his office is a modest, untidy, basement broom-cupboard.
And an overheated one at that, caused, he explains as he shows me in, by the hot water pipes that pass across the low ceiling en route to warm up his boss, Cardinal Cormac Murphy-O'Connor, who presides above stairs in Archbishop's House, a huge, dark pile in Victoria that is about as welcoming as a faded railway hotel in a period of national mourning.
There is, in this subterranean den, just about space for two chairs. They are tucked between the mini organ that, Father Seed reveals, someone has dumped in here, and the desk, which has a telephone lead going into a closed drawer. "It's the only way to get any peace," he says, sitting down in one of the chairs.
Father Seed is a boyish 50-year-old priest with tousled hair, permanently red cheeks, a genial manner and a reputation for making converts to Catholicism. As well as the formidable Miss Widdecombe, his name has been linked (sometimes erroneously, but we'll come to that) with the reception into his Church of John Gummer, the Duchess of Kent, Alan Clark and – most recently – Tony Blair.
In 2006, it was revealed that Father Seed had regularly been celebrating Mass at 10 Downing Street for cradle-Catholic Cherie Blair and the couple's four Catholic-educated children. Did Tony attend too? Father Seed looks surprised that I even need to ask: "Of course."
I've taken the chair opposite, a comfy wooden number where, it becomes apparent, several of the aforementioned great and good have sat sharing their religious agonies with Father Seed. And not only the great and good. "I've had hundreds come and sit in that chair who want to become Catholic," he says. There's a sing-song quality to his voice, which goes up at the end of sentences. "All very quietly. And I do what I can." He pauses for a moment.
There is a beguiling stillness about Father Seed, and an unworldly gentleness. It's easy to imagine pouring your heart out to him. "I have had two lady priests sitting there," he reflects, using a rather old-fashioned form of words to refer to women vicars in the Church of England, "who I have received because they are fed up with being treated like dirt in their own Church."
In the recent history of the Catholic Church in this country, there have often been particular priests who became – usually by design – magnets for those seeking to change their religious allegiance. In the 1930s, for instance, when Evelyn Waugh, Graham Greene and Lord Longford headed a wave of high-profile names "coming over to Rome", as they would have put it, it was the formidable Oxford-based Jesuit Father Martin D'Arcy. He was every bit as much a public name as Father Seed is now.
Father Seed, though, is a friar, a member of a religious order that is part of the Franciscan family. So, while the Jesuits were founded as a quasi-military religious order to reconvert Europe after the Reformation, the Franciscans have an older, less aggressive mandate: to support those in need. That is how the man sitting opposite me sees his work: helping people through a spiritual crisis. Whether or not they end up converting is immaterial. "We are all Christians. And that's that. Therefore the pilgrimage we make is a movement of Christ, and if it is an authentic movement, we should be joyful about people becoming Catholic or Anglican or Methodist."
Was that what he told Tony Blair? Now, Father Seed enjoys something of a reputation as a face one sees at smart parties and book launches around London, where he is unafraid – unlike many guests – to talk to the gossip columnists who stalk the room. Indeed, it's hard to imagine him being afraid to talk to anyone. But, though he is ready to chat and isn't coy about mentioning those "names" who have already publicly revealed their connection with him, he has a great sense of propriety.
So, for example, he has made it clear repeatedly that he did not have anything to do with the reception of the Duchess of Kent into the Catholic Church. That was Cardinal Hume's doing. And he is extremely discreet when it comes to the important stuff. He will not comment on reports that he received the Tory minister, diarist and lothario Alan Clark into the Church on his death-bed. And he is equally tight-lipped about Tony Blair.
This shouldn't come as a surprise. If he was indiscreet, the queue of people wanting to sit where I am now would quickly disappear. Therefore, on the subject of his link with the former First Family, he begins by picking his words with care.
"I first met them in 1994," he recalls, "when Mr Blair had just become Leader of the Opposition. I was involved in an ecumenical event, the Big Banquet, where church leaders served food and drinks to an audience made up of two halves – one half drug addicts, prostitutes and the homeless, and the other half 'celebrities'. And I was put on the Blairs' table. I didn't expect it. My eyes popped out when I realised." He relaxes into the memory. "When I sat down, Mr Blair had a prostitute on one hand and a homeless lady on the other. I better be careful how I put that. And I was next to Mrs Blair. We discovered we had things and people in common. Later, he was to launch his policy on homelessness at The Passage [a Catholic centre for the homeless near Westminster Cathedral]. And," Father Seed adds vaguely, "there were more social involvements."
So how, I wonder, did the much-reported Catholic Masses at 10 Downing Street come about? "Well, ultimately through friendship," he replies. "I was a priest they knew when they moved into the cathedral's parish in 1997, when he was elected as prime minister. For the first years, they would come along to Mass as a family, either on Saturdays to the 6pm or on Sundays to the 5.30pm, or sometimes to the children's Mass at nine on a Sunday. Which meant that, after September 11, if you had been a crazy terrorist, you'd have known precisely where to find them if you wanted to attack them."
So he started going to say Mass in their flat above Number 11 Downing Street. Father Seed is eager to portray this special treatment not as a privilege, but as a kind of torture. "Mrs Blair" – he never uses their first names – "absolutely hated it. She hated not being able to go to Mass with everyone else."
It would have seemed logical, given this long-standing connection, for it to be Father Seed that Tony Blair approached about being received as a Catholic. "No, it was the cardinal," he corrects me, "but those things I don't talk about. That's where my drawbridge comes down. The cardinal owned it, and you've seen the result. Now there's no more speculation, which is wonderful."
Not everyone saw Blair becoming a Catholic as wonderful. "Oh yes," he sighs, rolling his eyes, "Ann." The outspoken Catholic convert MP made headlines by demanding that Blair should first confess his sin of not outlawing abortion – often regarded as the keystone of orthodoxy by a particular type of Catholic – before he was allowed into the club.
Father Seed, though, is keen to gloss over such a conspicuous lack of Christian charity on Widdecombe's part. "For some in the press," he continues, "it seems that Mr Blair's reception came in the end as a shock. Though there was no reason why it should. I suppose it is the phenomenon that Catholicism is seen as seriously naughty."
It is an odd choice of words. Catholicism is more traditionally seen as rather upright, moral and – at least in matters sexual – not in the least bit "naughty". Only when you are married, straight, in the missionary position, not using a condom and want to conceive a baby is about as naughty as it gets.
"I was asked to preach in the Tower of London," Father Seed counters, "on the 400th anniversary of the Gunpowder Plot. I think I was the first Catholic priest to get in – and get out." He has a nervous laugh. "And there is something about that; that Catholics were once about to blow up Parliament. There is still something mysterious and naughty about us. It is to our advantage. Catholics in this country are, in reality, a fairly conformist group, but we are still seen as nonconformist. Had Mr Blair become a Methodist, for example, I don't think there would have been the same reaction."
The question of Blair's timing, though, remains interesting. By leaving it until he had left office, there was a sense that Tony Blair was either embarrassed by his decision, or regarded it as improper for a Catholic to be prime minister. Hardly evidence that Catholics are conformist? "I don't think it is that," Father Seed corrects. "There are some good reasons why he did it when he did it, but they are more private. But the time was right. If it had happened while he was in office, it would have caused him more difficulty, that blurring of the public and the private. The same would be true if it had been immediately after he left office. By waiting, it was very dignified, very correct, very quiet. No announcement." Was he there at the private ceremony? "I can't say," he replies. I take it as a yes.
Despite his fame as a "fisher of men", as Roy Hattersley recently damningly put it, Father Seed's official position within Catholicism is as a priest of Westminster Cathedral, the neo-Byzantine mother church of English Catholicism. He has also been, for the past 20 years, the ecumenical adviser first to Cardinal Basil Hume and now to his successor.
Catholicism, it would be true to say, has had to be dragged reluctantly to the inter-church table. It was only in 1965, for example, that it stopped accusing the Jews of deicide. In July of last year, the Vatican's Congregation for the Doctrine of the Faith published a document that set out with uncomfortable clarity that other Christian denominations "cannot be called churches in the proper sense". Anglican orders – that is, the validity of its priesthood – are defined by Catholic doctrine as "absolutely null and utterly void".
Given the suspicions this background inevitably must arouse with other faith groups, I wonder out loud: doesn't Father Seed's extracurricular work with converts make an already difficult job a great deal tougher? It must be hard, after all, to build ecumenical bridges with other churches when they suspect you are only interested in poaching their members.
To his credit, he doesn't even blink at the suggestion. "It is," he agrees, "a paradox. Yes, I accept it is a total and absolute paradox. And I have never been comfortable with it." But, he offers by way of defence, he took on his official post as ecumenical adviser just at a time when the Church of England was moving finally towards ordaining women, and that meant he found himself in the front line when disgruntled Anglicans started coming over to Catholicism – which bans women's ordination – in droves. "It is certainly eccentric, though," he concedes.
The paradox, as he describes it, puts me briefly in mind of a double agent, but then I look at Father Seed and know it can't be true. He is one of those highly intelligent but essentially childlike men. Clever, open but naive.
Has receiving so many high-profile people into the Catholic Church damaged his personal credibility as an advocate of ecumenism? "There was a time," he recalls, "when the cardinal [Hume] had an open evening for Anglican clergy thinking of Catholicism. I set out 60 chairs in the Throne Room upstairs. In the end, 300 came. We had informed George – George Carey, the Archbishop of Canterbury – what we were doing, but it did cause tension." He says the last word through his teeth.
Does he get on with Carey, now retired? "I had a long chat with him recently and we became much more friendly," Father Seed answers diplomatically. "But of course it did [cause tension]. There were times when people got angry with me, but I was doing Cardinal Hume's bidding. It was easier for Anglicans to focus their anger on me."
It sounds as if the relationship between Hume (who died in 1999) and Seed was a close one. The cardinal reportedly used to call his protégé either Miss Marple – because he knew people's secrets – or Mr Fixit – because he knew everyone. "Whenever I'd go into his room, I'd say, "Could you spare me a minute?' and the cardinal would look at his watch and say, "Counting, 60 seconds, 59 seconds...'. But he loved to gossip. We had a lovely relationship."
Father Seed is making Basil Hume sound like a father figure. Or perhaps it is just that, having read Seed's autobiography, Nobody's Child, published amid great hullabaloo last year, I am imagining that he must always be on the look-out for a family. The book was his contribution to a genre known as "mis lit" and tells in graphic detail about the adoptive parents, Joseph and Lillian Seed, who brought him into their poor Manchester home after his own teenage, unmarried mother had given him up shortly after birth. Joe Seed, a prison officer at Strangeways, beat the young Michael unconscious, burnt his arms against the grate as a punishment, and, from the age of six, sexually abused him. Lillian, broken by her husband's depravity, repeatedly attempted suicide, finally succeeding when Michael was eight when she threw herself under a train. "Today, I still cry for the lonely frightened boy I was then," he has written.
The book is unusually candid – especially for a priest. Does he regret being so open? "I'm not glad I did the book," he says simply. "This is the problem of having a publisher as a very, very good friend. I have a problem saying no. I should have said no to him."
The publicity material that surrounded publication presented Father Seed's story as one of triumph over adversity, from abused child to the priest-confidant of the stars. "It made it sound like a Billy Elliot kind of thing," he acknowledges. "It is how you sell books. Ann [Widdecombe, herself now a successful novelist] helped with the editing. There is a lot in there that I didn't want to go in, but it did. I was persuaded. Again, I found it hard to say no. Ann said no to some things."
There was, though, a positive side, he says. "I must have received hundreds of letters from people with similar stories. At least 50 were from nuns who had suffered in a similar way." Again he stops and allows a silence, but I want him to make explicit what he seems to be hinting at. Is he saying that there is a link between escaping an abused childhood and feeling a vocation to religious ministry? "The result of my childhood always takes me towards family, and community. And, in a religious order, I have found a monastic family."
To lift the darkness that has descended on us, Father Seed proceeds to tell, in amusing if well-polished detail, how he came to be a Catholic priest, having toyed with the Salvation Army, Methodists, Anglicans and even a sect of Strict and Particular Baptists in Birkenhead. "They regarded mainstream Baptists as heretics, so would have seen Catholics as the Devil incarnate." It was a perfect grounding for a future ecumenical adviser.
He thought about marriage – seriously. "I had girlfriends when I was 16 and 17, but I eventually chose to take vows. It is the interior life they give me that keeps me going." His moment of epiphany came, he recalls, when he was 18 and working in an old people's home in Manchester. "There was a rag and bone man living there, and one day – this would have circa 1975 – he came back with a copy of the Salford Diocesan Catholic Directory, which he gave to me. Being at that time a Strict and Particular Baptist and a fundamentalist, I took it as a sign."
The young Michael Seed rang the telephone number listed for vocations, but misdialled it and ended up with a French missionary order. He makes it sound a bit like a Mr Bean adventure. He ended up training for the priesthood with them for three years, but all the time was sneaking away to sample other religious orders – the Dominicans, the Benedictines, the Carthusians. All rejected him on the grounds that he was too young to make a lifelong commitment. Eventually – after being given a leaflet by an elderly lady parishioner about the Franciscan Friars of the Atonement – he found his spiritual home.
There are only three members of what is properly called the Society of the Atonement ("We have SA after our name – like Salvation Army, or smart arse") left in Britain; Father Seed and two 70-year-olds. But its background – it was founded at the end of the 19th century by Anglican Americans who went on to become Catholics – is perfect for his own mixed-up spiritual search, and for his day job. It was one of the Society's founders, Father Paul Wattson, who in 1908 founded the Week of Prayer for Christian Unity, which today is a feature on the world ecumenical calendar. Father Seed will be alongside our church leaders when they mark the centenary of the Week of Prayer at Westminster Abbey on Friday.
The Society of the Atonement has its roots in the life and teaching of Saint Francis of Assisi, who rejected smart society and preferred to live on the margins. What would he have made of some of the parties Father Seed is seen attending? "That thought occurs to me every day," he concedes. "It's about keeping a balance. If I get invited, what do I do? I like people. And I find it hard to say no. But one has to be careful. I am very conscious of how it may appear, so now I go to parties less and less. I hope I am becoming more reflective now that I have reached 50."
His two bosses, Cardinals Hume and Murphy-O'Connor, have had occasion, he admits, to question whether he isn't too much in the public eye. "If I was photographed tomorrow with anyone well known, it is immediately assumed I am converting them. I recently happened to meet, at a function for a disability charity, Heather Mills. The next day in the Evening Standard there was a big thing saying she was converting. I can't win."
But surely there is a sense of winning when someone does "come over"? Father Seed frowns. "We are all Christians," he says. So denomination is just a detail? "More or less. It's a pilgrimage, but there is for me something unique in the deposit of faith in Catholicism. It's like a tree and we've planted this tree and it is Christ. Christ founded one community. We are all Catholic in that sense."
I presume he means Christian. "Well, we are all Christian, but Catholic means universal. There's something unique in Catholicism." It can, he concedes, have its challenges. "I'm not always happy. There are agonies and ecstasies. But that's normal, isn't it?"
Perhaps. Certainly normal for this room. Or, more precisely, for those who sit in this chair.
Details of events to mark Week of Prayer for Christian Unity can be found at www.ctbi.org.uk. The centenary celebration at Westminster Abbey on Friday 18 January begins at 5pm and is open to all. Peter Stanford edited Why I Am Still a Catholic, published in paperback by Continuum.