Vosper successfully defended the claim under the fair dealing doctrine, with the Court of Appeal deciding unanimously in his favour.

On 9 September 1971 The Mind Benders, a book critical of Scientology written by Cyril Vosper, a former scientologist of 14 years, was published by Neville Spearman.

At issue was whether the extracts in The Mind Benders constituted copyright infringement, and whether the information published in the book amounted to an actionable breach of confidence.

The lower court granted the injunction to prevent publication of the book, finding that there was a strong case for infringement.

Lord Denning, writing the leading judgment for the court, found that the defence of fair dealing applied to Vosper's book under section 6(2) of the Copyright Act 1956, which said: No fair dealing with a literary, dramatic or musical work shall constitute an infringement of the copyright in the work if it is for purposes of criticism or review, whether of that work or of another work, and is accompanied by a sufficient acknowledgment.In clarifying the doctrine of fair dealing, Lord Denning considered previous case law, and described a legal test for determining what would constitute a valid use of the defence: It is impossible to define what is "fair dealing."

[2] The Church of Scientology also attempted to ban the book in Canadian libraries by threatening the sue for libel.

[4] The case, and especially the judgment of Lord Denning, has been frequently cited as the leading interpretation of the fair dealing defence in the United Kingdom.

[8][9] Chief Justice Beverley McLachlin separated the fair dealing test into six factors based on Denning's judgment:[8]