Revealing mistake: When the Krays are boxing for the first time, their mum comes in to break them up. She runs up to the ring where a member of the crowd holds the middle rope lower to help her get in the ring. The problem is, he pulls the rope before he sees her making her way to the ring. It can't be a coincidence as he lets go as soon as she's in the ring. (00:26:30)
Factual error: If you look at the band playing in the Regal Club the night the boy's mother first visits, the night where they first bring on the donkey, you'll notice that the drum kit used by the drummer in the band is, from what we can see, a 1980's Pearl kit, far too modern. (00:39:00)
Factual error: Aunt Rose died in 1955 and not when Reggie and Frances were on their honeymoon. (02:44:35)
Factual error: The recruits' hair is far too long when they parade after being conscripted. In those days Army recruits practically had their heads shaved - sideburns were shaved off to one inch above the ear (Army regulations). Curiously, this applies to the Staff Sergeant too - his hair would barely be visible under his hat.
Audio problem: When Reggie threatens the man outside his club, Reggie's boyfriend runs at him shouting "You stupid bastard..." and he is restrained by the gang. His lips never actually say these words.