"The Da Vinci Code" author Dan Brown defended himself Monday in Britain's High Court against accusations he took material for his blockbuster conspiracy thriller from a 1982 book about the Holy Grail.

Michael Baigent and Richard Leigh, authors of "Holy Blood and Holy Grail," filed a breach of copyright lawsuit against Brown, claiming he appropriated their ideas and themes.

Both books hinge on the theory that Jesus married Mary Magdalene and they had a child, and their blood line survives to this day.

Baigent and Leigh are suing Random House, which also published their book. Random House denies their claim.

Brown, Baigent and Leigh were all in court for the opening of the case.

If the two writers succeed in getting an injunction barring use of their material, it could threaten the scheduled May 19 release of "The Da Vinci Code" film starring Tom Hanks and Ian McKellan.