Former prison governor Ian Acheson said Abedi’s past showed he posed such a danger he should have been held under tighter security conditions than the ones at the separation unit. Mr Acheson also warned that the assault “moves us closer to the day when a prison officer will be murdered on duty by a terrorist”, adding that it is only a matter of time. The Justice Secretary Ms Mahmood said at the weekend: “I am appalled by the attack of three brave officers.”