Last week, a trial began in London that has all the makings of an international event. Two historians, Michael Baigent and Richard Leigh, commenced their lawsuit against Dan Brown, the author, and Random House, publisher of Brown’s international bestseller, “The Da Vinci Code.”

Baigent and Leigh claim that Brown and Random House violated their copyright in a book published (by Random House) in 1982 titled “Holy Blood, Holy Grail.” They claim that Brown adopted several key concepts from this 1982 work in his current best seller. If they win, they could conceivably receive all of the profits from Brown’s work, prevent the sale of all remaining copies of “The Da Vinci Code” and even stop Sony from releasing the film version of the book.

The primary concept which Baigent and Leigh claim to have copyrighted is one central to Brown’s book, that Jesus married Mary Magdalene and that they had a child, whose descendants became European royalty. Under British law (and American law as well), neither ideas nor facts can be copyrighted, only the tangible expression of those ideas. This means that Baigent and Leigh must prove that Brown stole their written expression of this and other ideas.

Such an expression of an idea need not necessarily be the exact wording used by the two plaintiffs. Under British law if they can show that Brown used the “conceptual architecture” of their book, i.e. a special sequence of ideas expressed in the book, then they may prevail. This, however, will be hard to prove.

Brown, in order to defeat Baigent’s and Leigh’s claims, must prove that he didn’t use their conceptual architecture or prove that the ideas he used, such as the marriage of Jesus to Mary Magdalene, are facts. Interestingly, when Baigent and Leigh first published their book, it was suggested in the advertisements that the work was not fiction, but factual, and that authors were recounting a “true history.”

Now, the two authors must deny this in order to prevail. A related approach being used by Brown’s lawyers is that the concepts at issue, even if not factual, were not original to Baigent and Leigh, but derive from the earlier work of George Davis, a man who has been characterized by the English press as a “rebel theologian.”

Certainly, Brown and Random House cannot claim that they didn’t know of Baigent and Leigh’s book, another theoretically possible defense. For one thing, Random House published both books. Second, Brown appears to have acknowledged some debt to the earlier authors because the name of Brown’s villain, Sir Leigh Teabing, is a thinly described anagram of Baigent and Leigh. Brown may well regret that bit of whimsy.

More than money is at stake in this case. If Leigh and Baigent win, many authors and publishers fear that the decision will become the basis for more such lawsuits and chill the production of new works based on earlier ones. Some have said that if Baigent and Lee win the precedent would mean that, were Shakespeare alive today, he’d have a copyright problem since his works, too, were derivative.

The case continues this week as the literary and legal world watches. We shall see where it goes. When it’s finished, I’ll report back.