Every country has been tempted on occasion to produce tendentious accounts of its history and particularly in the biography of national heroes. In extreme cases there can be actual manipulation of documentary evidence, but much more common is casual misrepresentation to justify someone's behaviour or perhaps to comfort national pride. Where a presumption of deceit is obvious, the damage is no worse than marginal: for example when a crucial but ambiguous letter from King Victor Emanuel to Garibaldi in 1860 was reproduced in half a dozen different versions, or when the execution of Mussolini in 1945 was described in many irreconcilable accounts by presumed eyewitnesses who had private axes to grind. On other occasions a reader is easily alerted to the chance that an author or editor might be trying to ingratiate himself with a powerful patron. But in many cases authenticity is hard to verify and there may be difficulty in deciding if a memoir or diary, whether for political reasons or to make a more saleable book, has been ‘improved’ or partially rewritten.

An easy method of falsifying written history is simple concealment of relevant facts, and here a particular problem in Italy is that cabinet ministers illegally used to retain important official documents after leaving office. Di Revel in 1867 was told by colleagues that this was a normal procedure and he should follow suit for his own self-protection. Sometimes indeed it was done with a deliberate intention to further someone's career by concealing information from whoever replaced him in government.