Each Saturday evening, in the privacy of his modest bedroom in north London, he removes his shirt and reaches for a five-tailed whip. Quietly intoning a recitation, he starts to scourge his back.

The cords bite painfully into his flesh, but again and again the erect figure lashes himself.

A devout Shi’ite? A sado-masochist? No, not at all. This is John Henry, a former professor of accident and emergency medicine at St Mary’s hospital in west London and an expert on drug abuse.

Henry has given evidence to parliamentary inquiries and is a regular commentator in the media. His spiritual life has been a more private affair but he confirmed last week that — like Ruth Kelly, the cabinet minister — he is a member of Opus Dei, the controversial Roman Catholic society.

There are tiers of membership. Kelly is a “supernumerary”, the second tier, who are allowed to marry. Henry is one of the “numeraries”, who make Opus Dei their family. They live with other members, remain celibate and practise “corporal mortification”.

Henry was recruited by Opus Dei in his twenties while living at one of its London student residences. He has given it most of his earnings throughout his working life.

His devotion entails not only the weekly whipping but also daily acts of self-denial, such as refusing a glass of water when thirsty. He wears a spiked chain, which Opus Dei calls a cilice, around his thigh for about two hours a day. “Pope Pius XII said it’s important to be a Christian and have the cross in your life,” he said. “It means you have to suffer in some way.”

All this would have remained a private matter were it not for the sudden revival of a decades-old controversy about the purpose and influence of Opus Dei.

Transferred in the cabinet reshuffle to a job that includes responsibility for implementing the equality act, which bans discrimination on the grounds of sexual orientation, Kelly faces flak for her membership of an organisation that condemns homosexuality.

More melodramatically, the imminent release of the film of The Da Vinci Code has put the spotlight sharply on Opus Dei and what some say are its suspect beliefs and practices.

Even Opus Dei’s most bitter critics agree that The Da Vinci Code book — which depicts it as a murderous cabal that conceals the true story of Jesus — is nonsense. But the bad publicity has spurred the organisation to come out fighting.

What is the truth? Is Opus Dei a secretive, reactionary cult or is it a well-meaning group of Christians who deserve credit for their good works and spirituality?

OPUS DEI means “God’s work”. With 86,000 members worldwide, it describes itself as “a personal prelature of the Catholic church that helps people seek holiness in their work and ordinary activities”.

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