The authors suing Dan Brown are "in danger of making fools of themselves", a court has heard.

Literary agent Patrick Janson-Smith told London's High Court the case was prompted by plans to make a film based on The Da Vinci Code. He added: "I thought the legal case was all a storm in a teacup."

Michael Baigent and Richard Leigh claim Brown stole ideas from their book, The Holy Blood and the Holy Grail.

Referring to when he first heard the allegations, Janson-Smith said: "While I saw similarities between The Da Vinci Code and The Holy Blood and the Holy Grail, I never thought there was a copying issue to deal with."

He continued: "They were most especially concerned that a film of The Da Vinci Code would jeopardise the chances of a film of The Holy Blood and the Holy Grail ever being made."

The film version of The Da Vinci Code, starring Tom Hanks, will receive its premiere at Cannes Film Festival in May.

Brown has denied borrowing ideas and specific words and phrases from the other book, though he admits referring to it for details.