Jack Dunn has long claimed that extensive portions of his novel, The Vatican Boys also appear in Brown’s book and that there are many similarities in the text, characters and plot points of the two works.
The Vatican Boys was written and copyrighted in 1997, while The Da Vinci Code was released in 2003.
In a letter to Penguin Random House, Mr Coad stated that unless a credible explanation is offered for the “hundreds of similarities” between the two books, copyright infringement proceedings will be commenced.
"Jack was a very diligent client," he said. "He sent over an initial analysis which we worked on until we had what I believe to be compelling evidence that he is right about his book being copied.“
"I found the response sent by the Random House lawyers less than entirely convincing. It seems to me that there remains a question mark over how many instances there are where the two books overlap which I find hard to attribute to coincidence. Our two barristers were in no doubt that copying had taken place. We will consider the response send by Random House and decide on next steps."
Mr Dunn added:
"The response we received from Random House was weak in that it relied heavily upon the US decision that saw me sue Random House and Dan Brown. In that case, the presiding judge ignored laws we gave him regarding structure copying. These were identified in the 2007 JK Rowling decision by Federal Judge Robert Patterson in Manhattan where he cited several laws regarding the copying of the structure of the story. In my case these laws were relevant to the structure of my story in The Vatican Boys being copied, by Dan Brown, into The Da Vinci Code. Also, in the Random House response to us in the UK, they correctly state and document that in the HBHG trial, Dan Brown did not list The Vatican Boys in his bibliography of the books he and his wife Blythe used to write The Da Vinci Code nor refer to The Vatican Boys in his testimony, during trial. If we were successful in proving our case that he did copy The Vatican Boys, this would pose a very serious problem for Dan Brown."