An inmate at Highpoint Prison held six members of staff hostage with a plastic knife embedded with razor blades a court has been told.
Lee Twyman, 28, barricaded himself and his victims in an office at the Stradishall jail on May 12.
He was serving an indeterminate sentence with a minmimum of four and a half years for public safety after being convicted of aggravated burglary at Canterbury Crown Court in 2012.
On Wednesday he was given a further 16 months in prison to run concurrently after pleading guilty to false imprisonment.
Michael Crimp, prosecuting, said Twyman had been caught with illegal items including wrappers for mobile phone SIM cards but disciplinary action was not taken against him because of an administrative mix-up.
Other inmates voiced suspicion about the lack of action against him and he was faced with threats which led him to ask to be locked into his cell for his own safety.
He was moved to another wing of the prison but again faced threats and confided in a support worker that he planned to grab officers’ keys to force his move to a higher security prison.
Before the support worker was able to report what he had been told Twyman went into an office and produced a plastic knife with razor blades embedded into it and took four prison officers and a mental health nurse hostage.
Another officer who walked into the office was also prevented from leaving although Twyman did, after 15 minutes, allow four staff to leave when two officers volunteered to stay with him.
Twyman barricaded the door, smashed mugs and let off fire extinguishers during a three hour stand-off but gave up after negotiators were called in.
Vanessa Halai, representing Twyman, said he had been assessed by a psychiatrist who concluded he was suffering from an emotionally unstable personality disorder.
“At the time he was suffering from emotional stress over what was happening and his mother was also receiving threats. He felt he had no other way out.”
In hindsight he would have acted differently she said.
Judge David Goodin told Twyman, who is currently held in Belmarsh Prison, that circumstances of the incident had been ‘peculiar’.
He warned him that the crime would have to be taken into account when he was eventually considrered for parole.