It is one of the bestselling novels of recent times. But of all the 40 million or so readers who have romped through Dan Brown's "The Da Vinci Code," none may be as important to the author, his book, and the world of fiction as Peter Smith.
The British judge has been perusing the 600-pager over the past week - not as part of his local reading group, but as part of a crucial copyright case in which two other writers claim that Brown stole their ideas.
Michael Baigent and Richard Leigh are suing Mr. Brown's publisher, Random House, alleging that the 2003 thriller was based on their 1982 historical work, "The Holy Blood and the Holy Grail," which contends that Jesus Christ survived crucifixion and escaped to France to sire a dynasty with Mary Magdalene.
If Brown's novel had readers on the edge of their seats, the case has copyright lawyers and historical authors similarly engrossed. For it touches on the very nature of the creative process of writing, questioning whether authors have free rein to rework the ideas and research of others.
In short, can history be copyrighted?
Experts say copyright generally protects writers from having their work reproduced verbatim. This protects them against "cut-and-paste" merchants reproducing chunks of their text word for word. But when it comes to ideas, concepts, facts and historical information, it's a different matter.
"Ideas aren't protected under English law," says copyright expert Robin Fry of the London law firm Beachcroft Wansbroughs. "The paradox here is that you can have a 600-page book and someone steals one paragraph and that's a copyright breach, but if you steal the whole basis of the book, then that's not a breach."
As the case began last week, Random House's lawyers argued that the two plaintiffs could not claim ownership of general material pertaining to the legacy of Christ. Their lawyer, John Baldwin, said the two authors were seeking "to monopolize ideas at such a high level of generality that they are not protected by copyright."
Experts tend to agree, feeling that the plaintiffs will have a hard time proving their case. "They have done this research for their book and are saying these are the facts," says Lorna Brazell, a copyright lawyer with the international firm Bird and Bird. "The problem is that a fact is information in the public domain and available to anyone who wants to use it for creative purposes."
There is a precedent that might work in the plaintiffs' favor. A 1980 case found in favor of a nonfiction author, Trevor Ravenscroft, who sued another writer for plagiarizing his work, "The Spear of Destiny." But in that case, the court decided that the guilty party, James Herbert, had copied language, characters, and incidents.
In the Dan Brown case, the plaintiffs are alleging only that the author lifted the "architecture" of their work, that is to say the central historical hypothesis of a Christian dynasty emerging in southern France that was viewed as a threat by the Roman Catholic Church.
While Brown's novel does indeed draw from this conjecture, his lawyer says the theory is by no means original to "The Holy Blood and the Holy Grail," known in court as HBHG.
And there are plenty of themes that appear in HBHG that do not appear in Brown's novel - and vice versa.
But Baigent and Leigh's lawyer says that the essence of the case against Random House is that Brown has not just allegedly borrowed facts, but has "lifted the connections that join the points up."
In a bizarre twist, a different division of Random House is the publisher of HBHG. A third author of "The Holy Blood and the Holy Grail," Henry Lincoln, has not joined the lawsuit.
Brown has acknowledged that many source materials inspired his work. He may even have introduced a clandestine, anagrammed acknowledgement to Baigent and Leigh by calling one of his characters Sir Leigh Teabing.
In August, he won a separate case against another writer, Lewis Perdue, who claimed "The Da Vinci Code" copied elements of two of his novels.
Julian Barnes, a British author whose "Arthur and George" also relied on assiduous historical research and is currently riding high in US bestseller lists, says it would be "calamitous" to deny authors the freedom to research, retell, and reinterpret ideas.
After all, even Shakespeare borrowed heavily from history.
"This is how a writer instinctively operates," he says. "It's just the same as if you've been told a story by a friend or something happens in your family. It's all fair game."
For his own "History of the World in 10-1/2 Chapters," for example, Mr. Barnes says he needed a character to make a journey to Turkey in the 1850s.
The best way to bring this to life was to look up works by travelers of the time. "So you use some of their stuff and try to rewrite it," he says.
"It would be a calamitous case if the 'Holy Blood' men won," he adds.
Ms. Brazell, the copyright lawyer, agrees. She says a verdict in favor of the plaintiffs would be "a huge setback for people whose source material for creating fiction is other people's historical or sociological research."
"What we are protecting is the material that's available for the creative imagination to work on," she says.
There are parallels with other art forms. You can't patent a chord, and even in art there is a surprising amount of scope for reproduction. "If you were fond of [John] Constable's 'The Haywain,' and set up in the same spot and reproduced it, you haven't breached copyright, because you have taken it from nature," Brazell says.
Ironically, even if they lose, Baigent and Leigh may have achieved something from their quest.
Copyright is, after all, an economic right, and some financial redress has already emerged from a not altogether unexpected source.
Online bookseller Amazon reported that sales of "The Holy Blood and the Holy Grail" shot up 3,500 percent the day after the trial began.
"Copyright normally works by proving someone else has got the income that you deserved," says Mr. Fry, the copyright expert.
"This is not the case here. I'm sure the Dan Brown book has been a huge boost to sales of 'The Holy Blood and the Holy Grail.' The judge will be influenced by that."
Or, as Barnes puts it: "My instinct is that this case wouldn't have happened in the first place if 'The Da Vinci Code' hadn't been very successful."
The case continues Tuesday, and Brown may take the stand this week with a verdict expected soon thereafter.