When Albert Pierrepoint is on his way to execute Dorothea Waddingham, he is carrying a gas mask case. Dorothea Waddingham was executed in 1936, 3 years before the Second World War, therefore he would not be carrying a gas mask.
There was a close-up shot of Pierrepoint's hand at one point showing quite clearly a plain gold wedding band. It was customary in Britain at this time for men to wear no ring signifying that they were married. If they chose to wear a ring, it was usually a signet ring. Plain wedding bands came in much later from the 60s onwards.
In the final sequence of the film, when Pierrepoint is typing his letter of resignation, the last words are shown, as they are typed, to be "executioners forthwith." However, when Pierrepoint signs the letter in the next shot, the word "Executioners" is shown with a capital E.
When Annie Pierrepoint is sitting in bed checking the 'accounts', she refers to a "job at Strangeways" for which Albert was not paid. He recalls that the prisoner received a very late reprieve, and Annie indignantly talks of him "going all that way down there for nothing". Strangeways is not "all that way down there". It is in Manchester, the city where the Pierrepoints lived.
The Hamelin war criminal hangings took place in an execution chamber at the end of a cell corridor within the old prison itself, not in an aircraft hangar. Pierrepoint described this very clearly in his memoirs.
The film meddles somewhat with the chronology of Pierrepoint's career. The execution of Polish murderer Piotr Maksimowski, accurately shown to have been performed in the record time of 7-and-a-half seconds, took place not in the immediate post-war period before Pierrepoint took the lease on his pub; but years later on 29 March 1950 - nineteen days after the higher-profile (and later infamous) hanging of Timothy Evans. Furthermore, the man who served as assistant executioner on both occasions was named Syd Dernley, not George Cooper.
Weights of the condemned being expressed in the American way as pounds, rather than the British stones and pounds. Pierrepoint was most meticulous, and would have based all his executions on the UK Home Office table of drops for hanging, which uses British units.
The title, "The Last Hangman" is misleading and incorrect. Albert Pierrepoint was not the last hangman in the U.K. Harry Allen and Robert Leslie Stewart were the last hangmen when capital punishment was last applied in Britain in 1964.
Nowhere in Pierrepoint's autobiography does he mention 'Kirky' or George Cooper. Similarly in the film, there is no presence of Steve Wade, Syd Dernley, or Harry Allen, who were Albert's assistants on many occasions.
During the Belsen crew execution scene, a total of four women are shown being hanged. In the Belsen trial only three women - Irma Grese, Elisabeth Volkenrath and Joanna Bormann - were sentenced to death and executed.
When taking the height and weight measurements of Erma Grese for hanging, she snaps to Pierrepoint and Lieutenant Llewelyn in only slightly accented English. Yet at the foot of the gallows, when Pierrepoint speaks to her in English, Llewelyn must translate to German for her. Grese's outburst in English may have been artistic licence, but verisimilitude would have been better served if she's spoken in subtitled German.