American author Dan Brown copied from an earlier book to produce his blockbuster novel, The Da Vinci Code, it was alleged yesterday.
It was only because the High Court judge who heard the copyright case did not understand the law that he got away with it, three appeal judges were told.
High Court judge Mr Justice Peter Smith in April last year cleared Brown of copyright infringem
ent of ideas set out in The Holy Blood and The Holy Grail (HBHG).
Now two of the three authors of HBHG have taken the case to the Court of Appeal, claiming the theme of the book that made Brown the highest-paid author in history was taken from their 1982 work.
Jonathan Rayner James QC, representing authors Michael Baigent and Richard Leigh, told Lords Justices Mummery, Rix and Lloyd that Brown had "strenuously denied" copying from HBHG.
He said that although Mr Justice Peter Smith had found that Brown's wife, Blythe, had "extensively" relied on ideas in HBHG in researching her husband's book, there had been no copyright infringement.
"The appellants' case was that the theme appropriated by the Browns and used in DVC (The Da Vinci Code) was a substantial part of the appellants' copyright work and was, thus, an infringement.
"The judge, however, considered the case to be about whether the central theme (of HBHG) was itself a protectable copyright work.
"This error led the judge into a series of judgments that were wrong in law and the judge then misapplied the law to his extensive findings of fact.
"When the law is properly interpreted and is applied to the judge's findings of fact, the only proper conclusion is that the defendant has infringed the appellants' copyright."
The defendant in the case is not Dan Brown, who was a witness at the High Court hearing, but Random House, publishers of both DVC and HBHG.
But Mr Justice Peter Smith said at the end of the High Court case: "In reality Mr Brown is on trial over the authorship of DVC."
Mr Rayner James said his clients were seeking to protect their skill, judgment and labour in creating HBHG.
"Their case is that others should not be permitted to appropriate that skill, judgment and labour for themselves as Mr Brown has done in the writing of DVC."
Mr Justice Peter Smith ordered that Baigent and Leigh should pay 85 per cent of Random House costs which were estimated at nearly £1.3m. They also have to pay their own legal costs.
HBHG deals with a theory that Jesus and Mary Magdalene married, had a child and the bloodline continues to this day, with a secret society protecting their heirs against wicked conspiracies enacted by the Church.
It is similar to the theme explored in the Brown novel which has earned the author hundreds of millions of pounds worldwide since its publication in 2003.
Brown said the accusations were "completely fanciful" and HBHG was just one of the works studied for his novel.
