In 1983, a German magazine Stern published with an exclusive report on what would have been one of the biggest stories in history: a sixty two volume collection of diaries written by Adolf Hitler.
The diaries were found by Gerd Heidemann a reporter, who bought them, with the magazines money, for over £2.5 million. The diaries passed three authenticity tests using its handwriting; the Times of London and Newsweek engaged historians Hugh Trevor-Roper and Gerhard Weinberg to examine the papers, with Trevor-Roper convinced of their authenticity. But Stern was too afraid the sensational story would leak, and so refused to allow any German experts on World War II to examine the diaries. Within two weeks of publication, the West German Bundesarchiv had exposed the Hitler diaries as "grotesquely superficial fakes" made on modern paper using 1980s-era ink and riddled with historical inaccuracies. Many editors of Stern, the Sunday Times and Newsweek lost their jobs. The diaries were discovered to be the the work of notorious Stuttgart forger Konrad Kujau. Both Heidemann and Kujau went to trial and were each sentenced to 42 months in prison for forgery and embezzlement.
If you want to read more, I found a more detailed explanation of the story here: http://www.unmuseum.org/hitlerdiaries.htm