But first a new drama: The Da Vinci Code is about to be played out in the courtroom in a case which could prove every bit as gripping as Dan Brown's blockbuster.

Tomorrow, the world's biggest-selling adult book will become the subject of intense legal wrangling at London's High Court as two authors will claim that Brown cannibalised their hard research to create his blockbuster The Da Vinci Code.At stake will be millions of pounds of publishing profits and a threat to the film's release date.

With sales of 40 million and counting since it was published in 2003, Dan Brown's book has become an international phenomenon, generating millions of pounds worth of publishing and tourism spin-offs. A film version starring Tom Hanks, as the dynamic code-cracking Prof Robert Langdon, and Audrey Tautou has been completed and due for release in May.

But writers Richard Leigh and Michael Baigent are claiming that the book plagiarises the concepts they wrote about in their non-fiction tale The Holy Blood And The Holy Grail, written 20 years earlier.

At the heart of the case is the theory that Jesus Christ did not die on the cross, but married Mary Magdalene and had a child, starting a bloodline that was protected by the Knights Templar, as detailed in Leigh and Baigent's book.

Brown's Da Vinci Code is also based on the notion that Jesus married Mary, starting a family in France where their descendants continue to live.

The authors have said that there have been "huge chunks" of The Da Vinci Code which have been simply taken from their book. The case is important because it could establish principles for how freely authors may use the research of others for fictional works.

Brown, who is expected to fly in from his home in New Hampshire to give evidence during the trial, has already acknowledged a debt to the writers in the pages of his book.

He makes reference to their book which is lifted from a shelf by the character Sir Leigh Teabing (an anagram of Baigent).

Responding to the claims of plagiarism, Brown has said the "information has been out there for a long time and there have been a lot of books about this theory".

If successful, the authors will seek a slice of the profits from the book. The case also threatens to impact on the release of the movie version of The Da Vinci Code . . . which is due to be released on 19 May in most parts of the world, shortly after a screening at the Cannes Film Festival . . . until a deal has been thrashed out.