This week, Mr Valero will have his hands full as he attempts to separate fact from astonishingly popular fiction. The might of Hollywood is lined up against him as the film version of The Da Vinci Code is released worldwide. Starring the most successful film actor of his generation, Tom Hanks, and directed by Ron Howard, who has a string of blockbusters to his name, The Da Vinci Code is set to gross hundreds of millions of dollars worldwide. To cap it all, it is based on one of the most successful novels of all time, sales of which have rocketed to 60.5 million worldwide.
The Da Vinci Code claims that Opus Dei is a secretive, all-powerful sect within the Catholic church which controls the Vatican and the world's financial markets. In the book a murderous albino monk from Opus Dei tries to stop a Harvard professor from discovering the clues that suggest Jesus had a child with Mary Magdalene.
At Mr Valero's plush Notting Hill residence, which doubles as the headquarters of Opus Dei in Britain, he revealed his strategy to The Independent on Sunday. "I don't take the film or the book seriously," he said. "It is rubbish, theologically. But I do take the readers and the viewers seriously. There is one thing wrong with this film - it is trading fiction as fact."
Sony Pictures, which has made the film, has been asked to run a disclaimer at the start labelling it as a work of fiction. The film's director, Ron Howard, last week refused the request. "Spy thrillers don't start off with a disclaimer," he said. "This is a work of fiction that presents a set of characters that are affected by these conspiracy theories and ideas. Those characters in this work of fiction act and react on that premise. It's not theology. It's not history."
But Mr Valero accused Howard of dishonesty. "Of course people know Tom Hanks is an actor and Robert Langdon [the character he plays] doesn't exist and the plot is invented. But people believe the background and all that is made up as well.
"Nothing in that story is true. This is the dishonesty of Ron Howard, Sony and Dan Brown. The trailer starts, "seek the truth". What kind of a beginning is this?"
Mr Valero's strategy for countering the film's claims is simple, he said. "We are going to be nice. Nice and positive and friendly. Instead of being the angry placard-waving Christians who spoil everybody's fun, Opus Dei is going to take a different approach."
Mr Valero, who joined Opus Dei at the age of 16 after seeing a sermon by its founder, Josemaría Escrivá, said the organisation should welcome the enormous success of the book and the likely success of the film. "This has given us a huge exposure," he said. "We couldn't buy this publicity. Opus Dei has become the best-known religious organisation in the country thanks to Dan Brown."
Mr Valero's public relations strategy could not be more different from the organisation's original response. When the New York division of Opus Dei was first warned about the novel, one of the organisation's directors said: "I wouldn't worry about it. It will never sell."
Part of the strategy will involve debunking the myths Opus Dei believes have been propagated by The Da Vinci Code.
Hanks last week said those objecting to the film were taking it too seriously. "The story we tell is loaded with all sorts of hooey and fun kind of scavenger-hunt-type nonsense. If you are going to take any sort of movie at face value, particularly a huge-budget motion picture like this, you'd be making a very big mistake."
That has not stopped senior Roman Catholics calling on Christians to boycott the film. Archbishop Angelo Amato, a leading official at the Vatican, called for people to reject the film's "lies and gratuitous defamation". In the Philippines, a senior government official has called for it to be banned.
But Opus Dei and other parts of the church have been careful not to call for a boycott of the film. In Britain, a Da Vinci Code Response Group has been set up, headed by Austen Ivereigh, the director for public affairs of Cardinal Cormac Murphy-O'Connor, the Archbishop of Westminster and head of the Catholic church in England and Wales. The group has said it does not believe in boycotts. Mr Valero said: "This is an opportunity to teach. Not a fighting moment; a teaching moment."
When Opus Dei was set up in 1928 its aim was to encourage Catholic people to live every aspect of their life through the prism of their religion. Josemaría Escrivá, a priest from Madrid who founded the group, believed too many Catholics separated their every-day lives from their religion. In particular, his book The Way advocated "holiness through work".
During the organisation's early days it had strong links to the fascist regime of General Franco and has always been seen as a conservative grouping within the Catholic church. The sect runs more than 100 technical and management schools across the world. Major corporations including Cisco Systems and Vodafone sponsor courses. Marjorie Scardino, chief executive of the media group Pearson, sits on the advisory board of one of the business schools in Spain.
But according to John Allen, a Vatican analyst who has written the first full investigation into Opus Dei's global activities, the reality is very different from the Dan Brown-inspired myth.
It is a very small organisation within the Catholic church with just 86,000 members worldwide, including only 500 in Britain. The total global value of all its assets is $2.8bn - roughly the same size as the Archdiocese of Chicago or Milan. While Brown's novel claims that Opus Dei pulls all the levers in the Vatican, Mr Allen said just 20 out of 2,650 people in the papal bureaucracy are Opus Dei members. Of the world's 4,500 Catholic bishops, 40 are in Opus Dei.
Allegations that Opus Dei controls the world's financial markets prompt howls of laughter from Mr Valero. "It is great, isn't it? I can press a button now and whoosh, the country goes to pot."
Mr Allen said: "The Opus Dei of reality is a lot less interesting than the Opus Dei of myth. While Opus Dei has some limited influence it has no more, in fact, than any other group of its size within the Catholic church. Charges of secrecy over the years are mainly due to their reluctance to say anything publicly."
Nevertheless, for such a small organisation Opus Dei clearly punches above its weight. Pope John Paul II certainly held the group in high esteem. He canonised Escrivá just 27 years after his death - a record.
Dan Brown insists that the depiction of Opus Dei within the novel is "fair and balanced". He said it was based on interviews he conducted with past and present members.
"There may be those who are offended by the portrayal," he said. "While Opus Dei is a very positive force in the lives of many people, for others, affiliation with Opus Dei has been a profoundly negative experience."
Secrecy is just one of the criticisms levelled at the organisation. It is accused of being homophobic, something that has put the government minister Ruth Kelly under renewed pressure. In this month's cabinet reshuffle, Ms Kelly, who has admitted receiving "spiritual support" from Opus Dei, was given the equalities brief. When asked whether she believed homosexuality is a sin, Ms Kelly refused to answer.
"What we believe is no different from what millions of people believe," said Mr Valero. "We are not in favour of any discrimination against anybody for what they are," he insisted.
One of the most eye-catching claims about members' behaviour is so-called "corporal mortification" or self-flagellation. Numeraries - members who are celibate - wear a spiked garter, known as a "cilice", around the top of their thigh for two hours a day.
"Numeraries wear it if they want as a penance and as a mortification," said Mr Valero. "It is rough, you notice it there. But it causes discomfort, not pain. It is a traditional thing that has been used in the church for a long time."
If Opus Dei's strategy is successful, the number of Britons putting on the cilice will grow. Already, Mr Valero claims, every day is bringing new membership inquiries. Perversely, the release of the film may only increase the organisation's influence.
"Historically Opus Dei has always been the bad guy," said Mr Allen. "Now, for the first time, they get to cast themselves as the victim. They are a small Catholic group that is being beaten up by big, bad Hollywood."
Beliefs & Practices: Banned books and chastising the body
Celibate members, known as "numeraries", wear a spiked garter - a "cilice" - around the top of their thigh for two hours daily. Wearers of the cilice say it causes discomfort but doesn't draw blood. Numeraries also whip their back or bottom with a small piece of rope "for the purpose of chastising the body and reducing it to servitude".
Between 20-30 per cent of members are celibate. Many live in single-sex Opus Dei housing. The majority, known as "super-numeraries" can marry, have children and live in their own homes.
Numeraries are expected to donate a proportion of their salary to the organisation. They take enough for basics including food and housing but hand over the rest. Critics have claimed Opus Dei targets highly paid professionals in order to secure more funding.
Opus Dei's founder, Josemaría Escrivá, believed too many Catholics "leave their Catholicism at the door" when they go to work. He argued that a Christian should act in accordance with the religion in all ways; to seek to "sanctify himself or herself through situations that are part of their daily life" and not just when they go to church.
Some former members of Opus Dei have claimed that they were forbidden from reading certain books by the sect. The forbidden titles included some books that were on the reading lists at Catholic universities. Opus Dei argues that it merely offers "advice" to its members and that individuals are always free to take it or ignore it at will. Books that the sect "advises" members not to read include anything considered pornographic, violent or "anti-religious".Reuse content