The Day of the Jackal (1973)

Plot hole: An important plot point (in the book and the film) is that Charles Calthrop - thought to be the Jackal, at that stage - played some mysterious part in the 1961 assassination of Rafael Trujillo, the dictator of The Dominican Republic, and rumours of his involvement came to the attention of MI6 and Special Branch, leading to the accidental exposure of the Jackal's false passport. In fact there is no mystery at all about the assassination of Trujillo and there were no shadowy foreigners involved. It was organised by Trujillo's own senior aides, amongst them General Juan Tomás Díaz, Antonio de la Maza, Amado Garcia Guerroro and General Antonio Imbert Barrera. The gunman was later identified as Luis Aniama Tio. All the conspirators except Tio were arrested, tortured, and shot. There was no panicked evacuation of foreigners who were involved with Trujillo's regime, and no reason for them to be concerned - the government did not fall and Trujillo's brother Hector took over as President, ruling in a brutal and totalitarian manner for a further eight years. Any rumours of a mysterious Englishman would have been dismissed out of hand and would not have made it onto even the lowest level filing system anywhere in Whitehall.

Lebel: It's obvious that the Jackal has been tipped off all along, and yet he's decided to go ahead, regardless. He's simply challenged the whole lot of us.
Minister: Are you really suggesting that there's a leak from inside this room?
Lebel: I can't say. But we think that the Jackal is now in Paris with a new name and a new face, probably masquerading as a Danish schoolteacher.