The position of the manhole cover changes from shot to shot when the police lift it after Evans' "confession" - first it's seen (as it was in real life) in the middle of the road opposite No.10 with the front door to the house closed but, in the next close-up shot, it's being lifted from a position in front of the bay window of a house further down the street, with the front door of (supposedly) No.10 open.
In the pub scene where Beryl and Tim agree to have the abortion done, Tim is seen drinking from an almost full glass of ale; after the cut, the glass is almost empty, then it's almost full again in the next shot.
When Tim Evans is in the café in Wales, he looks down at the police station opposite, as if from an upstairs window. The camera cuts to a shot from the street and he is clearly on the ground floor on a level street.
When Tim first goes to the police to confess disposing of his wife's body, in the long shots his hair is neatly combed back from his forehead, but in the close-ups, his hair is hanging loosely over his forehead.
Christie pastes only the middle of the wallpaper he uses to hide bodies in the wall. When he hangs it, however, the edges stick to the wall.
Timothy and Beryl Evans are shown as already having their baby daughter Geraldine when they first take the flat, whereas in reality she was not born until after they had lived there for six months.
Christie's medals - he enlisted in 1916 and therefore could never be eligible for the 1914-15 Star he wears (red, white and blue ribbon), he could only have been awarded the War and Victory medals.
The caption '1949' appears on the screen as the Evans family come to view the top floor of 10 Rillington Place, but in fact they moved in in 1948.
At the beginning of the film Christie is wearing his medal ribbons for 1914-18. They are back to front, first should be 1914-15 Star, then War Medal and finally Victory medal. The rainbow watered ribbon for the Victory medal is first on his tunic, it should have been last.
The time taken for executioner Albert Pierrepoint to hang Timothy Evans is far too long. According to Pierrepoint's wiki entry, "from entering the condemned man's cell to opening the trapdoor took him a maximum of 12 seconds".
When Christie is explaining the procedure he's about to perform on Beryl, he says that natural gas contains carbon monoxide, then quotes its formula as CO2 (which is actually carbon dioxide). The correct formula for carbon monoxide is CO. However, the point appears to be to show him for the half-educated conman he is. It's just Christie's character creating an air of "expertise".
When Beryl's bound and bundled body is discovered by police, the cord is cut and her legs freely stretch out. That could not have happened in reality since rigor mortis would have long set in. Also, no mention is made of the odor that would have been noticeable. *Although rigor mortis sets in a few hours after death, it dissipates completely after 48 to 60 hours, depending on the ambient temperature. This amount of time is about what is depicted in the film.
When Christie is murdering Muriel Eady he uses a breathing mask as a gas mask connected to the cooking gas mains, over Muriel's face. But just as she begins to succumb her nose appears above the mask, which would allow her to breathe normally.
When Christie is talking to Beryl in the kitchen about abortions , there is no steam coming out of the kettle as he fills the teapot. Presumably the crew did not want to risk anyone getting scalded, but there was no need to include the kettle/teapot in the scene.
After Timothy Evans' sentence is upheld by the medical board, a hand is shown writing "The Law must take its course" on his file. The 'its' is written as 'it's' - the contracted form of 'it is'.
Christie was arrested by a policeman on the embankment overlooking the River Thames on 31 March 1953, i.e., early spring. However, in this scene the trees nearby are in full foliage (late spring-early autumn) when in reality they would have been bare leaved.
When Christie is about to be arrested, several buses can be seen passing across the bridge in the background. They are all "Routemasters", a type that didn't start coming into use until 1956, three years after the events being depicted.
At the end of the film where Christie is arrested, the police constable leads him away from Putney Bridge (seen in the background). Putney police station is, in fact in the opposite direction in the Upper Richmond Road. The direction the constable takes Christie in the film would only lead down the river towpath towards Hammersmith.
Christie is wearing a police uniform when Muriel Eady comes to the house in the opening scenes but he had already long left the police by this time. Muriel would have known this as she and Christie met when they both worked for the same employer.
Beryl Evans is portrayed by Judy Geeson with a middle class accent when in reality she was working class & spoke Cockney.