Steve Vander Ark, the creator of a Harry Potter encyclopaedia, who is on trial for plagiarism, broke down in the witness box on the second day of evidence in the case.

Vander Ark, 50, who created 'The Harry Potter Lexicon' out of material taken from his popular fan website, itself based on the series, told a New York court of his devotion to the Harry Potter books and denied the allegations, claiming his book was a reference guide intended as a companion to the series.

Asked if he considered himself a part of the Harry Potter fan club community, the librarian broke down in tears and said: "I do. It's been difficult because there's been a lot of criticism, obviously... but it has been an important part of my life for the last nine years or so."

Vander Ark, whose lawyers claim his book constitutes a 'fair use', a legal concept, of the Potter material, said he wrote the book after requests from Harry Potter fans.

He claimed he did not use quotation marks or refer to Rowling as the author because, "It’s a reference book. If I was writing a reference book to Shakespeare, I wouldn’t list Shakespeare."

On Rowling’s own plans for a Harry Potter encyclopaedia, the proceeds from which she will reportedly donate to charity, he added: "I for one can’t wait to read it."