The written judgement contained a series of italicised letters

Mr Justice Peter Smith has explained how to crack the code in his 71-page ruling after two newspapers claimed to have solved it.

The message read: "Smithy Code Jackie Fisher who are you Dreadnought."

The judge admires Admiral Jackie Fisher, who developed battleship HMS Dreadnought, which launched in February 1906, 100 years before the case began.

In a statement, Mr Justice Smith said: "The message reveals a significant, but now overlooked event that occurred virtually 100 years to the day of the start of the trial."

"I hate crosswords and do not do Sudoku as I do not have the patience," he said.

He added that the preparation of the code took 40 minutes, with its insertion in the text taking the same length of time.

Mr Justice Smith said a typographical error had been added deliberately to "create further confusion".

Ancient sequence

The Da Vinci Code, which has sold more than 40 million copies worldwide, features a number of codes the heroes of the book must crack to solve the mystery.

Mr Justice Smith had earlier said he intended it as "a matter of fun".

His entry in Who's Who lists him as a fan of Fisher, who is credited with modernising the British navy.

Mr Justice Peter Smith (right) presided over the Da Vinci case

The judge had told The Guardian and The Times that the code was based on the ancient Fibonacci number sequence, which is used by the heroes in Brown's novel.

In March, Mr Justice Smith presided over a High Court case brought by authors Michael Baigent and Richard Leigh, who claimed Dan Brown plagiarised their own historical book, The Holy Blood and the Holy Grail.

But Mr Justice Smith ruled Mr Brown did not substantially copy Mr Baigent and Mr Leigh's work, saying it did not have a central theme in the way its authors suggested.

A film version of the novel, starring Tom Hanks as historian Robert Langdon, is released on 19 May.