The judge who presided over the failed Da Vinci Code plagiarism case at London's High Court hid his own secret code in his written judgement.
Audrey Tautou and Tom Hanks will star in The Da Vinci Code film
Seemingly random italicised letters were included in the 71-page judgement given by Mr Justice Peter Smith, which apparently spell out a message.
Mr Justice Smith said he would confirm the code if someone broke it.
"I can't discuss the judgement, but I don't see why a judgement should not be a matter of fun," he said.
Italicised letters in the first few pages spell out "Smithy Code", while the following pages also contain marked out letters.
Although he would not be drawn on his code and its meaning, Mr Justice Smith said he would probably confirm it if someone cracked it, which was "not a difficult thing to do".
In March, he presided over a High Court case brought by authors Michael Baigent and Richard Leigh, who claimed Dan Brown plagiarised their own historical book for The Da Vinci Code.
But Mr Justice Smith ruled Mr Brown did not substantially copy Mr Baigent and Mr Leigh's work The Holy Blood and the Holy Grail, saying it did not have a central theme in the way its authors suggested.
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.
A much-anticipated movie version of the novel, starring Tom Hanks as historian Robert Langdon, is released on 19 May.