A lawyer for author Dan Brown has told the High Court that claims he stole ideas for The Da Vinci Code have been left "in tatters".
Random House published both books at the centre of the dispute
John Baldwin QC, representing publisher Random House, said the evidence made it a "travesty" to say Mr Brown lifted from The Holy Blood and the Holy Grail.
Michael Baigent and Richard Leigh claim Mr Brown plagiarised their book.
Summing up the case, Mr Baldwin said the ideas were "not original" and "too general" to be protected by copyright.
Mr Baigent and Mr Leigh claim Mr Brown's best-selling novel "appropriated the architecture" of their non-fiction work, The Holy Blood and the Holy Grail, published in 1982.
Both books explore the theory that Jesus married Mary Magdalene, that the couple had a child and that the bloodline survives.
Lawyer Mr Baldwin told the judge that the earlier work did not have "anything like the importance" to Mr Brown's book that the authors had claimed.
Mr Baldwin said that before Mr Brown read The Holy Blood and the Holy Grail, he had written a synopsis for The Da Vinci Code which contained "most of the ideas complained of".
He said: "The claimants' case is now in tatters.
"It is true that Mr Brown cannot recollect exactly which source or sources he used for any particular point.
Dan Brown's The Da Vinci Code has sold 40 million copies worldwide
"But since his clear evidence was that he did consult the sources he referred to and this evidence was not challenged, the court cannot conclude that he copied The Holy Blood and the Holy Grail."
Mr Baldwin claimed the claimants' case would fail "even if Mr Brown had taken these ideas".
"The ideas are of too general a nature to be capable of copyright protection," said Mr Baldwin.
"Many of the ideas complained of were not original to The Holy Blood and the Holy Grail. They were merely copied from others.
"The claimants were doing themselves exactly what they complain of in Mr Brown."
New Zealand author Michael Baigent is one of the co-claimants
The lawyer said Mr Brown had been "a good witness" but Mr Baigent was "thoroughly unreliable" while giving evidence.
Mr Leigh's evidence should "be approached with considerable caution", he added.
The hearing was adjourned until Monday, when closing submissions on behalf of Mr Baigent and Mr Leigh are expected to be made.