Britain's High Court was plunged into the arcane world of Templars, Merovingians and characters such as Pepin the Fat as lawyers argued Tuesday over the genesis of the mega-selling thriller "The Da Vinci Code."

A lawyer for the novel's publisher said ideas about the life and legacy of Jesus Christ that two writers claim were stolen for Dan Brown's blockbuster are so general that they are not protected by copyright, and that many key themes of their book are not in "The Da Vinci Code."

"We say that's fatal to their case," said John Baldwin, lawyer for publisher Random House.

Michael Baigent and Richard Leigh, authors of the 1982 nonfiction book "The Holy Blood and the Holy Grail," are suing Random House, Inc., claiming that parts of their work formed the basis of Brown's 2003 novel, which has sold more than 40 million copies and has been made into a film starring Tom Hanks.

They say that Brown "appropriated the architecture" of their book, which explores theories that Jesus married Mary Magdalene, that the couple had a child and that the bloodline survives.

Random House, which also published "The Holy Blood and the Holy Grail," denies the claim.

If the writers succeed in securing an injunction to bar the use of their material, they could hold up the scheduled May 19 release of "The Da Vinci Code" movie, directed by Ron Howard. Sony Pictures said it planned to release the film on time.

Lawyers for the two claimants said Monday that the book's third author, Henry Lincoln, is not participating in the case, and asked the court not to infer anything from his absence.

Laying out his opening arguments, Baldwin said that the claim by Baigent and Leigh "relates to and seeks to monopolize ideas at such a high level of generality that they are not protected by copyright.

"A lot of the points are in a lot of other sources," he said.

Brown, a resident of New Hampshire who rarely speaks to the media, is expected to testify next week; he sat silently in court on the second day of the trial. The case was later adjourned until next Tuesday so that the judge, Peter Smith, can read both books and related texts.

Brown's mystical thriller follows fictional professor Robert Langdon as he investigates the murder of an elderly member of an ancient society that guards dark secrets about the quest for the Holy Grail and the story of Jesus.

The book's mix of code-breaking, art history, religion and mystical lore has won millions of fans around the world, but has also endured plenty of controversy, including criticism from the Catholic church, ridicule from scholars and a previous copyright lawsuit that was decided in favor of Brown.

Baldwin said many important themes of "The Holy Blood and the Holy Grail" are not featured in "The Da Vinci Code," particularly the idea that a secretive order called the Priory of Sion, linked to the medieval Knights Templar, seeks to restore Jesus' descendants — the Merovingian dynasty — to the thrones of Europe. Among their enemies in the book is Pepin the Fat, a seventh-century official.

Similarly, the idea that Jesus' crucifixion was faked "is an important element of their book" that "forms no part of 'The Da Vinci Code."'

In Brown's book, Jesus does not survive the crucifixion. Brown said Monday that questioning Christ's death and resurrection "undermines the very heart of Christian belief."

The claimants say they developed the idea that Jesus fathered a royal bloodline from medieval documents including the "Dossiers Secrets," found in France's national library in Paris.

The theme was taken up by the authors of many other books, including Brown.

Jonathan Rayner James, a lawyer for the plaintiffs, said Monday that his clients were not attempting to claim a monopoly on ideas or historical debate, but to prove Brown had "relied heavily" on the earlier work, published in Britain in 1982 and the following year in the United States.

Baldwin said Brown developed most of the central ideas of his book independently.

"He found the ideas that he wanted to use in his novel before either he or his wife had looked at 'The Holy Blood and the Holy Grail,"' Baldwin said.