Michael Baigent and Richard Leigh, authors of the best-selling non-fiction book "Holy Blood, Holy Grail," claimed that, in his Da Vinci Code novels, Dan Brown had stolen some of their key ideas and therefore had violated their copyright.

Their book, which appeared in the early 80s, expounded the idea that Jesus and Mary Magdalene married and had children together, and that the blood line of their descendants had been consciously preserved to this day, with a secret organisation dedicated to protecting it.

This idea did form the kernel of Brown's novels. However, British courts rejected the suit, insisting that information, ideas, and theories were not covered by the concept of copyright. As a result of the judgement, which they appealed, also losing the appeal, Baigent and Leigh were left with a legal bill amounting to several million pounds, and were ordered to pay 85% of the defendant's costs.