Factual error: On his arrival at Longmarsh Prison, Danny Meehan is told that the establishment is a 'Cat B' prison. However, earlier in the plot, we learn that Danny Meehan is to be sent to a 'high security' prison. Cat B prisons are not high security prisons. They are known as 'local' or 'training' prisons. 'Dispersal' or 'Cat A' prisons form part of the high security estate.
Factual error: Mr. Hayter is introduced as the Chief Officer of Longmarsh Prison. The position or 'rank' of Chief Officer disappeared in 1987, 14 years before the movie was released.
Factual error: Danny Meehan is sentenced to 3 years, at London Crown Court, for assaulting police officers and drunk driving when banned. He could not have gone to the crown court for these offences. They are summary only offences and would remain in the magistrates' court. Additionally, the maximum sentence, as the offences arose out of the same set of circumstances, would be 6 months imprisonment maximum (in totality). Also, there isn't an offence of drunk driving when banned. This would be 2 offences; driving with excess alcohol and driving whilst disqualified.