By Torin Douglas
Media correspondent, BBC News
This is the first time the Reynolds defence has been applied to books
The author of a book about police corruption has won a ground-breaking libel case in the Court of Appeal.
Three judges found in favour of Graham McLagan and his publisher, Orion, overturning an earlier judgement against a former Flying Squad officer, Michael Charman.
That ruling found that Mr Charman had been libelled in the book Bent Coppers - The Inside Story Of Scotland Yard's Battle Against Police Corruption.
Judges have now ruled that the book was covered by the so-called "Reynolds defence" of qualified privilege, which says that journalists can publish material in the public interest, even if it turns out to be untrue and defamatory, provided it has been handled responsibly.
It's the first time it has been applied in the case of books.
Lord Justice Ward, Lord Justice Sedley and Lord Justice Hooper said they were "totally satisfied" that the book was a piece of responsible journalism.
They said the author had demonstrated his honesty, expertise, careful research and painstaking evaluation of a mass of material.
Mr McLagan is a former BBC correspondent, who has covered police corruption issues for 20 years. Speaking from the US, he said it was "a victory for solid, responsible investigative journalism".
Caroline Kean, a partner at his solicitors Wiggin, called it a ground-breaking case.
"This judgement is a breath of fresh air, building on a decision last year by the House of Lords involving the Wall Street Journal," she said.
"That judgement expressly stated that the defamation laws should encourage, rather than discourage, serious and responsible journalism."
The Reynolds defence is named after a House of Lords judgment in a case brought by former Irish Prime Minister Albert Reynolds against the Sunday Times in 1998.
Lord Nicolls, who gave the leading judgement, laid down 10 points which courts might take into account when deciding whether to admit a plea of qualified privilege.
They included the seriousness of the allegation, the source, and the responsibility of the journalism - the steps taken to verify the story, the urgency of the matter, whether the claimant was asked to give his side of the story, and the tone of the article.
Ms Kean said that, in subsequent libel judgements, some courts had treated these as "hurdles", each of which had to be cleared if the Reynolds defence were to be accepted.
The Bent Coppers ruling, and the one in favour of the Wall Street Journal, meant this was no longer the case.
"This is an unambiguous confirmation by the Court of Appeal that Reynolds is alive and kicking and it is not limited to newspapers," said Ms Kean.
"It applies equally to a book and, by analogy, it will apply to a film or a TV programme, providing it is something of proper public interest and a journalist has done his very best to act in the course of responsible journalism."
Mr Charman, a former Flying Squad officer, was supported in his libel claim by the Police Federation, which now faces costs estimated at more than £1 million.
The judges said that £400,000 must be paid on account within 28 days.