Dan Brown today entered the witness box to reject claims that he stole ideas for his blockbuster novel The Da Vinci Code, branding the allegations "completely fanciful".

In a scathing attack on the two authors accusing him of plagiarism, Mr Brown said they made "sweeping statements" which "astounded" him and were "simply untrue."

The millionaire author appeared at the High Court in London to defend his publisher against claims that his internationally successful thriller novel lifts from The Holy Blood And The Holy Grail, a bestseller itself after it was published in 1982.

Mr Brown's evidence served to offer an intriguing glimpse into what inspired him to construct the plot of his book which has captured the imagination of millions.

Mr Brown, who said he thought about giving up writing before embarking on his breakthrough novel, said that his wife carried out much painstaking research for the book.

Both books under the spotlight explore theories that Jesus married Mary Magdalene and then had a child with her, thus creating a surviving bloodline. Mr Brown's novel has created a phalanx of spin-off books and documentaries.

Authors Michael Baigent and Richard Leigh are suing The Da Vinci Code publisher Random House for copyright infringement, claiming that Brown "appropriated the architecture" of their novel.

Mr Brown’s fast-moving theological thriller has sold more than 40 million copies since it was published three years ago this week. Publicity from the ongoing court case appears to have produced a surge in sales for The Holy Blood and the Holy Grail too since the trial began, going from about 350 copies sold a week in Britain to 3,000, according to trade publication, The Bookseller.

Mr Brown said much of the research for the book was done by his wife, Blythe, saying that she was "deeply passionate about the sacred feminine". But the 41-year old author, who has travelled from his home in the United States, said that The Holy Blood And The Holy Grail was just one of many book he had studied.

In a statement put before the court, Mr Brown said: "Messrs Baigent and Leigh are only two of a number of authors who have written about the bloodline story, and yet I went out of my way to mention them for being the ones who brought the theory to mainstream attention.

"I have been shocked at their reaction. Furthermore I do not really understand it."

He added: "The documents contain numerous sweeping statements which seem to me to be completely fanciful. I would like to restate that I remain astounded by the claimants’ choice to file this plagiarism suit."

Mr Brown also gave an insight into his routine a writer, saying that he viewed creative writing as "a discipline" that required constant practice and honing of skills. He said: "For this reason, I write seven days a week. So my routine begins at around 4am every morning, when there are no distractions."

Mr Brown said that his love of codes was inherited from his father, a mathematics academic, and he would spend hours when he was a child working out anagrams and crossword puzzles.

Instead of receiving presents at Christmas, his parents would leave a treasure map with clues which, if properly solved, would lead to a secret location in the house or even around the town where they lived, the court heard. He said: "It was wonderful fun - for me codes and treasure hunts have always been a passion."

Speaking of what led him to write the novel, Mr Brown explained that one of the novel's themes was "secret history", those parts of the past which had been lost or twisted by historical revision or subversion. He said: "This blend of fact and potential intrigues me and is one of the reasons I love Leonardo da Vinci."

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