The Freemasons' Code: Dan Brown reveals the message that told him the door to the lodge is open

His best-selling novels illuminate the shadowy organisations that supposedly run the world. But Dan Brown was “honoured” to receive an invitation to join the Freemasons, the arcane fraternity whose tentacles are said to extend into the highest echelons of power.

Tonight the Da Vinci Code author made a rare public appearance, discussing his latest Dante-inspired blockbuster, Inferno, in front of 1,500 fans in London.

The choice of venue, Freemason’s Hall, the headquarters of the United Grand Lodge of England, reflects the author’s fascination with the male-dominated medieval society, founded in London, which has long been the centre of conspiracy theories about its supposed global influence.

“I would be honoured to be a Mason,” Brown told the Independent before the event. “You don’t get ‘invited’ by the Masons but they sent a clear message that the door is open if I ever want to join.”

Brown’s 2009 novel The Lost Symbol suggested that the government in Washington was secretly run by a coven of Freemasons practising sinister rites.

However Brown said: “I’ve nothing but admiration for an organisation that essentially brings people of different religions together, which is what they do."

“Rather than saying ‘we need to name God’, they use symbols such that everybody can stand together.”

Everybody except women, who are refused entry. “I guess it’s a little oxymoronic,” said Brown. “But there are certainly women’s organisations and I think there’s a place for men to be together alone.”

Brown portrayed Opus Dei as a sinister Catholic cult in the Da Vinci Code. Inferno introduces The Consortium, a secretive organisation pulling strings behind the scenes which the book claims is an amalgamation of real groups. Yet Brown sees the Masons as an entirely benign fraternity.

“Freemasonry is not a religion but it is a venue for spiritual people to come together across the boundaries of their specific religions,” he said. “It levels the playing field.”

The author’s only hesitation before undertaking the notorious Masonic initiation ritual is that he would have to take a “vow of secrecy” and would be unable to utilise his masonic insights in future novels.

Inferno sold 228,000 hardback copies during its first UK week on sale. The figure does not include ebooks which can now account for more than 50 per cent of sales. Brown holds the record for the fastest-selling UK hardback with The Lost Symbol, which sold 550,946 copies during its 2009 opening week.

Already tipped to be the year’s best-seller, Inferno sends Harvard professor of symbology Robert Langdon on a chase through Florence, Venice and Istanbul, to prevent a deadly virus from spreading across the globe.

The body count remains low and Brown is concerned that violence in popular culture is a factor in the recent spate of US high-school shootings.

“I don’t put in anything that’s gratuitous,” Brown, 48, said. “I think video games are very dangerous,” he said. “The quantity of hours that people play these first person shooter games. It becomes a reality of some sort, and that’s a part of it.”

“It really comes down to educating schools and parents. To say ‘you know what, you can’t play that, sorry, I’m just not going to let you do it’.”

Brown adds: “In the US it’s kind of funny that you can see brutal violence on television but sex is taboo.”

Reviewers called Inferno, which presents Langdon with a series of puzzles inspired by Dante’s Divine Comedy, “clunky” and repetitive. But the author would not swap his 200 million sales for a positive critique. “You wish they loved you but when they don’t life goes on. I just write the book that I wanna read. I’m here for my fans not the critics.”

The book suggests that a new Black Death-style “cull” might be the most effective way of dealing with an imminent population crisis. “I was absolutely staggered when I learned that in the last 85 years the population has tripled – that’s 200,000 new people every day,” the author said. “It’s a big problem it will require a big solution and that may be one of them. We may want to step in and do it in a more humane way than nature is going to.”

Inferno also gives Brown an opportunity to renew hostilities with the Catholic Church over its attitude to contraception. “I only mention the Vatican once and that’s just to say we’ve got a problem and it’s a dangerous policy to say we should not manage our numbers.”

Despite the furore which The Da Vinci Code provoked from Catholic groups, Brown has become something of a pin-up with nuns. “A lot of nuns wrote to me and said ‘Thank you for pointing out that we have dedicated our lives to Jesus Christ and we are still not fit to stand behind the altar. We’ve given up everything for Jesus and because we’re women, we can’t participate behind the altar.’”

The church should reconcile itself to gay marriage too. “I think that everyone should have the exact same rights regardless of their sexual orientation or anything else.”

Although he has no plans to retire Langdon, Brown would like to find a way to take the character to Asia in future instalments. He may also launch an entirely new literary franchise, write a “techno thriller” or publish a straight historical biography.

If you spot an anonymous figure perusing a historic landmark in the UK’s capital, it could well be Brown conducting his undercover research. “London is still a treasure trove of Robert Langdon potential,” he said. “I don’t talk much about what I’m working on next but of course the UK is an incredible spot. I definitely will be back in my baseball hat and glasses.”