Frederick Forsyth's 1971 novel "The Day of the Jackal" remains an immortal political thriller that defined the 'assassination novel' in popular consciousness. What has always intrigued me is the small but significant Charles Calthrop plot-element. This was a person in the novel whom police agencies supposed to be the real identity behind the Jackal. Wikipedia notes that
Charles Calthrop is the name of a former small-arms salesman who was in the Dominican Republic at the time Rafael Leónidas Trujillo was shot. The SIS later heard a rumour that Calthrop has helped the partisans kill Trujillo by shooting the driver of his armoured car, causing it to crash. In the book, the British police originally think Calthrop is the Jackal's real name, until the real Calthrop shows up at the end, after the Jackal's assassination attempt was thwarted. The authorities were misled by the fact that chacal (i.e., Cha[rles] Cal[throp]) is French for "jackal".
The main Wikipedia article elaborates that
Lebel does everything he can to discover the Jackal's identity. He first calls upon his "old boy network" of foreign intelligence and police contacts to inquire if they have any records of a top-class political assassin. Most of the inquiries are fruitless, but in the United Kingdom, the inquiry is eventually passed on to the Special Branch of Scotland Yard, and another veteran detective, Superintendent Bryn Thomas.
A search through Special Branch's records turns up nothing. However, one of Thomas's subordinates suggests that if the assassin were an Englishman, but primarily operated abroad, he would most probably come to the attention of the Secret Intelligence Service. Thomas makes an informal inquiry with a friend of his on the SIS's staff, who mentions hearing a rumour from an officer stationed in the Dominican Republic at the time of President Trujillo's assassination. The rumour states that a hired assassin stopped Trujillo's car with a rifle shot, allowing a gang of partisans to finish him off. Additionally, Thomas also learns that the assassin was an Englishman, whom he is able to identify as Charles Calthrop (...)
Checking out the name of Charles Calthrop, Thomas finds a match to a man living in London, said to be on holiday. While Thomas confirms that this Calthrop was in the Dominican Republic at the time of Trujillo's death, he does not feel it is enough to inform Lebel, until one of his junior detectives realises that the first three letters of his Christian name and surname form the French word for Jackal, Chacal (...) the Special Branch raids Calthrop's flat, finding his passport, and deduce that he must be travelling on a false one (...)
[Epilogue] In London, the Special Branch are cleaning up Calthrop's apartment when the real Charles Calthrop storms in and demands to know what they are doing. Once it is established that Calthrop really has been on holiday in Scotland and has no connection whatsoever with the Jackal, the British are left to wonder "If the Jackal wasn't Calthrop, then who the hell was he?"
In short, the name of Calthrop cropped up in a high level international enquiry about the possible real identity of the Jackal, but the police became excited about its possibilities when the person was found missing and his name parts seemed to spell out "cha-cal" which is French for "jackal".
Ironically the Jackal was probably unaware of the name Calthrop and never used it as an alias, as far as I can recollect. However, what was revealed as false coincidence at the very end, actually energized the search for the Jackal, and gave the police focus and hope: in particular, the discovery of Calthrop's passport in his house created the impetus to look for recently faked or stolen passports and led them to discover the Jackal's assumed identities through genuinely good detective work, which in turn helped the authorities launch a massive manhunt that put him under various forms of pressure.
So how important was the Charles Calthrop element in foiling the assassination? Did the wild coincidence mean pure bad luck for the Jackal, or was the investigators' policy of following up every possible lead (especially persons of interest who were untraceable during that crucial time window) simply an example of good and meticulous detection?
[Please include adequate references to support your answer, so as to avoid any objection of being "primarily opinion based."]