From the outside, Netherhall House in Nutley Terrace is a bland 1960s student block, tucked away in one of the maze of streets that tumble down the hill from London's leafy Hampstead Heath to the A41 dual carriageway. But behind the unassuming façade, Netherhall House is one of the few public faces of Opus Dei, the secretive Catholic sect regarded by many outsiders as sinister and misguided.
Last week, for the first time since the organisation was founded in 1928, Opus Dei was given its own parish by Cardinal Cormac Murphy-O'Connor, the Archbishop of Westminster. And in April, Father Gerard Sheehan - one of 17 British Opus Dei priests in Britain - will take over pastoral care of St Thomas More Church in Swiss Cottage, north London.
But this respectability within the Catholic Church has been achieved against a background of controversy. With the publication of Dan Brown's bestseller The Da Vinci Code last year, Opus Dei emerged as less trustworthy than Satan and about as welcome in the wider church as the serpent in the garden of Eden. The publicity helped to transform this corner of north-west London into a tourist destination. You can now book (for around $3,000 including flight from the States and accommodation) Da Vinci Code tours.
"We've had coaches of Americans turning up outside, standing there staring through our windows," says Jack Valero, a Spaniard with a Kilroy tan in his early forties. Valero is the public face of Opus Dei in Britain. "You can imagine what they must think is going on inside, but I'm afraid they'd be very disappointed if they could see what you're seeing."
Valero is taking me on my own private tour of Netherhall House, and, as he implies, there's not a dead body, a scheming albino monk to rival The Da Vinci Code's Brother Silas, or a lost descendant of Mary Magdalene in sight. Indeed there are no women at all because this is an all-male facility. Opus Dei likes to keep the sexes apart - save for when Netherhall needs cleaning, when female members are permitted to come in to tidy up after the chaps.
What you do see a lot - in the chapel, in the library, in the meeting room - are sugary portraits of Opus Dei's founder, Monsignor Josemaria Escriva de Balaguer, a Spaniard who died in 1985 and was declared a saint by Pope John Paul II in 2002.
The Polish pontiff evidently has a very different impression from The Da Vinci Code readers of this 85,000-member-strong international organisation started by Escriva in the time of Franco. For John Paul it is a bastion of true Catholicism, accorded by him the unique status of a personal prelature, putting it in effect above Catholic law and structures, dependent solely on the Pope. There is an irony in an organisation that prides itself on following to the letter Catholic teaching being in effect given its own Get Out of Jail Free card.
Yet from the Vatican's point of view, it represents an extremely good deal. In Opus Dei it has found, to its evident relief, a strong, mainly non-clerical (only two per cent of members are priests) voice echoing its own opposition to contraception, sex outside marriage, abortion, condoms and stem-cell research amid a chorus of indifference or downright opposition to such teachings from most Western Catholics. When these à la carte Catholics demand reform of the official line, the Pope has only to point to Opus Dei to show that not everyone rejects the set menu.
And John Paul is not alone in his appreciation. Ruth Kelly, the new Secretary of State for Education, is reportedly an associate of Opus Dei. She is certainly listed (alongside William Dalrymple, Rocco Forte and Stephen Pound MP) as one of the guest speakers in the Netherhall House annual report.
In the face of protests that her links with such a conservative religious body make her unsuitable to be Britain's headmistress, Kelly has so far remained silent. Opus Dei meanwhile refuses to give out information about its members - exacerbating the impression of a Mason-like secrecy - but those who have met Kelly in private confirm that she is enthusiastic in her praise for the organisation, anxious to put her associates in touch with it (part of the duties of members is to recruit among their social contacts) and utterly humourless when challenged about its more bizarre practices. Some numinaries, as members are known, choose for example to wear a medieval metal chain with spikes round their thigh, with the spikes sticking into them, as a way of mortifying their sinful flesh.
Part of the extreme reaction to Kelly's connection to Opus Dei recalls the suspicion that lasted long after the Reformation that Catholics can never be loyal servants of the crown, that they are in hock to an overseas power with an agenda to force their extreme views on the rest of society. Today, a mention of Opus Dei, thanks in no small measure to The Da Vinci Code, plays readily to those age-old fears. It is foreign, Spanish to boot, so virtually a second Armada. It is secretive. It is part of the Pope's inner circle. And it has an apparently bottomless purse for buying up prime locations around London.
It all chimes with the worst stereotypes of Catholic subversives from Guy Fawkes onwards. In his obituaries, it was claimed that Cardinal Basil Hume, the gentle Benedictine monk who was head of the English Catholic Church until his death in 1999, had lain to rest such ghosts, but the Kelly affair shows they still seem to have some life in them.
However, it is around Opus Dei's recruitment measures that the most pressing concern is felt. Netherhall House, opened in 1967, offers upmarket accommodation to male students at London universities. Its residents come from 30 countries and only half are Catholics, Valero tells me proudly, as if producing the killer fact that disproves every allegation against Opus Dei. Yet this is accommodation with strings attached. First, there's the sort of Catholic regulations in force that turned Ireland against the church in the 1960s. No girls above the bottom stair (unless they've got a mop in their hand).
And then there's the odd, antiseptic feel to the place, as if all life has been drained out of it. Given that this is a student hostel, it is unnaturally quiet and tidy. I can't help thinking that it looks as if it has been arranged to look normal when really it is concealing terrible secrets. But I've clearly been reading too many Dan Brown books. Valero, for his part, makes no bones that the hostel is a kind of bait. Fishing is a term commonly used within Opus Dei for its crusade to attract young Catholics into its arms. Give them a comfortable place to live, show them Catholicism at its best and hope that the experience will inspire grateful residents to join up. "We hope simply being here and living as we do will enthuse them," is how he puts it.
For Opus Dei this is simply good old-fashioned evangelisation and they have no intention of apologising for it. Catholicism, they point out, was founded as a missionary faith, even if most modern mass-goers overlook the imperative to spread the Good News. For others, though, such activities are what gives the organisation, and by association the rest of the church, a bad name. Cardinal Hume was so concerned at its activities in Westminster diocese in the 1980s that he issued it with four recommendations. These demanded that no one under 18 should be allowed to join, that all recruits should discuss fully their decision beforehand with parents or guardians and be free at any time to leave without pressure, and that all Opus projects be clearly identified as such. Hume was a cautious man and would only have risked such a public clash with the papal cheerleaders if he had clear evidence that Opus Dei was doing all the things that he outlawed. My own experience in the 1980s was of meeting several youngsters who had arrived in the big city, felt utterly lost and were therefore vulnerable enough to rush into the arms of the Opus Dei student who had befriended them and offered them a friendly place to live, only later to regret it and embark on a damaging struggle to get free. It turned them off Catholicism for life.
Valero pooh-poohs such tales. He is a polished PR man. Before dedicating himself full-time to Opus Dei, he ran a successful computer company. He insists that all the mistakes of the past are now history, that Opus Dei has changed, but the opportunism certainly remains. So, for instance, when the Da Vinci Code trippers turn up outside, they are now invited in for tea. Officially it is to dispel the caricature of Opus Dei produced by Dan Brown - the courts might have been a more effective route - but you cannot help but see the potential for a bit of fishing in such apparently casual encounters.
Tour over, Valero ushers me into a side room with plush green leather chairs, and produces coffee and biscuits while swatting away with a smile the list of charges made against Opus Dei. I state these boldly, just in case he has his fishing rod hidden anywhere. It is said, I suggest, that you have too much money. He hands me a set of published accounts for one of the Opus Dei trusts in the UK showing receipts of £2.5m last year and reserves of £12m. It is a lot, he admits, but there is a lot to do.
What about the $50m office block you have just built in downtown New York with separate entrances for men and women, I ask. Nothing very secret about that, he counters, and looks straight into my eyes.
Only twice during our conversation does he avert his gaze. The first comes when we get on to the founder. Some who knew him say that he was a fraud who lied about everything from his real name to the extent of the Holocaust. His diaries, they say, were written with a view to presenting himself as saintly when the reality was that his actual interest in life was power and advancement in the church, a process completed by his followers after his death when they spent a lot of money on fast-tracking his cause for canonisation in record time.
"Nothing makes me angry any more," Valero says, staring out of the window, "but this thing about the Holocaust still does. It is all based on the account of one man. I don't know of anyone else who heard the founder say such things. It is a lie." The one man, it should be pointed out, is an ex-Opus Dei member who left and is now a senior priest in Westminster diocese. And one reason why the charge has stuck down the years is the context of Escriva's life and work. Opus Dei rose to prominence first in Spain under Franco's Fascist regime. Several ministers were closely linked with it.
Later I ask Valero about his own route into Opus Dei. His father was a member, he says, and at 15 he visited Rome and heard Escriva speak. It made such a powerful impression on him that at 18 he joined. He is not a priest, but has taken a vow of celibacy. Why, I ask. Again he is staring out of the window. "Because it leaves me free to travel where I am needed." But couldn't you do that with a family? "Not at short notice."
I cannot decide if my questions are unnecessarily prying, or perfectly reasonable in an effort to understand the strange world of Opus Dei. Its very name means work of God, and for members, life, work and relationships are all tools of evangelisation. Every encounter is a chance to make a new convert. You can see how a family would get in your way. And how prized a Cabinet seat will be.
So, saints or schemers? Good people under attack for being out of step with an increasingly secular society, or a cult-like sect with an ever-increasing network of well-placed members aiming to subvert the church and society? It may disappoint the sightseers, but it's probably neither.
Manipulative? Yes, especially in recruitment. Zealous? Undoubtedly, and that always unsettles us in such live-and-let-live times. Sinister? Probably more like unpleasant and sly in its casual sexism and determination to convert. Dangerous? Only in the same way that an overactive teenager is dangerous. Too much enthusiasm, too many black-and-white answers, too little tolerance. But teenagers grow out of it, and compared to the Opus Dei I knew back in the 1980s, there are certainly fewer pimples.