HE is believed to be the inspiration for the hero of Dan Brown’s bestselling novel The Da Vinci Code, and is credited with revealing the secrets of Rosslyn Chapel on which the cult book is based.

Now Dr Robert Lomas, who like Brown’s protagonist Robert Langdon is an international expert on symbolism and myth, is to publish a no-holds-barred account of the secret initiation ceremony of a freemason.

In Turning the Hiram Key, Lomas, of Bradford University, describes his own initiation at the Eaglescliffe Masonic Hall, where he was ordered to strip and put on “rough linen pyjamas” in the ladies lavatory by a man wearing a lambskin apron and holding a sword.

He includes details of the “contorted question and answer session”, during which he was asked to twist his body into strange positions while blindfold in a masonic temple, his trousers and sleeves rolled up.

At the completion of the ceremony the blind was ripped off and, half-blinded by the intense brightness in the room, he saw 40 white-gloved masons who clapped once to signify the end of his initiation.

The master of the lodge, wore an elaborate V-shaped collar of blue and white, the floor was covered in a white shroud, and the five-pointed star was shining on the eastern wall of the room, illuminating a skull and two crossed thigh bones.

The book, published by Lewis Masonic, explores the subsequent rituals, myths and symbolism of freemasonry that Lomas claims are connected to spiritual fulfilment.

However, his bid to go public has provoked outrage from fellow freemasons, who believe Lomas has betrayed the trust of the ancient organisation, first founded in Scotland in the 15th century.

Jim Munro, a Scottish freemason who gives tours of Rosslyn Chapel, said the revelations detracted from the ancient and mystic attraction of the clandestine order. “If anybody can buy it and read it on the bus eating a takeaway, then the essence of something ancient and mystical will die,” he said. “Lomas might have good intentions, but I really object to masonry being used as a tool to sell books.”

Another senior Scottish mason, who declined to be named, claimed that the attempt to uncover masonic secrets was “disgraceful”. He said: “The man has trivialised and made a laughing stock of an ancient and dignified tradition.”

Bob Cooper, the museum and library curator of the Grand Lodge of Scotland in Edinburgh, said Lomas could offer only a personal view of freemasonry. “I appreciate what he is trying to do. He feels freemasonry has been a positive influence in his life and that stimulating interest will benefit the craft,” he added. “But the danger is that in removing the mystique he is doing the opposite.”

However Lomas defended the book, which he claimed would set the record straight and would help to recruit new members. “It’s a major source of information about ourselves and our past that will disappear if we don’t get new blood in,” he said. “Previous exposés of freemasonry have been done by outsiders. As an insider, I’m saying this is a good thing. I’m trying to show what I got out of it.”

In 1996, Lomas claimed that Rosslyn Chapel was the hiding place for scrolls containing the secret teachings of Jesus Christ.

Freemasonry was founded in Scotland by the St Clairs of Roslin and the first minuted meetings were recorded in Edinburgh in 1599. Orders have since spread across the world.

Throughout the centuries thousands of famous men have been linked to the order including George Washington, the first president of the United States, Sir Winston Churchill and Mozart.

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