The authors of a 1982 book that raised the theory that Jesus Christ sired a dynasty of kings with Mary Magdalene are facing a £2 million legal bill after a court rejected their copyright claim against Dan Brown, author of The Da Vinci Code.

After one of the most closely followed trials in High Court history, Mr Justice Peter Smith ruled that American author Brown did not infringe the copyright of Michael Baigent and Richard Leigh when he wrote his worldwide bestseller.

Baigent and Leigh argued that DVC, as it has been referred to in the case, lifted the "architecture" of their earlier book, The Holy Blood and the Holy Grail (HBHG), which was itself a bestseller but never achieved anything like the success of Brown's book which has sold more than 40 million copies since its publication in 2003.

But in a 71-page ruling issued today, Justice Smith said that Brown did not copy the central theme for his novel from the earlier book. "The plaintiffs’ case has failed," he said. "Dan Brown has not infringed copyright. None of this amounts to copying The Holy Blood and the Holy Grail."

He added: "Even if the central themes were copied they are too general or of too low a level of abstraction to be capable of protection by copyright law. Accordingly there is no copyright infringement either by textual copying or non-textual copying of a substantial part of HBHG by means of copying the central themes."

The judge ordered that Baigent and Leigh should pay 85 per cent of publisher Random House's costs, estimated at nearly £1.3 million, as well as their own costs of £800,000. He said there should be an interim payment of £350,000 by May 5 and refused the authors permission to appeal his decision.

Brown said in a statement: "Today’s verdict shows that this claim was utterly without merit." Random House said that the ruling "ensures that novelists remain free to draw in ideas and historical research".

Gail Rebuck, chairman and chief executive of Random House, said: "Justice - and common sense - have prevailed. It is highly unusual and very sad that these authors chose to sue their publishers, especially after 20 successful years. This case has been extremely distressing for all concerned. The ruling is very important for the future of creative writing in the UK."

Leigh spoke briefly to a scrum of reporters outside the court. He said that he believed the claim had pitted "the spirit of the law against the letter of the law" and that he and Baigent had been vindicsted on the former. When asked to explain this comment, he replied: "I leave it to you to interpret."

Brown, meticulous in his 69-page witness statement but occasionally tetchy under cross-examination in court, admits that the book was one of dozens of sources he used, but says that he wrote his synopsis for DVC before ever reading HBHG, which he has still not got round to finishing.

Had Mr Justice Smith found for the HBHG authors in their claim against Random House, which published both books, the ruling could have delayed the scheduled May 19 release of the DVC film, starring Tom Hanks.

More importantly it would have stunned the world of copyright law by challenging the concept that copyright protects the expression of an idea rather than the idea itself.

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