Two men are being questioned under terror laws over an attack on a prison officer at HMP Whitemoor in March.
The pair, aged 24 and 26, were arrested on Monday (March 2) over the incident at the 458-capacity maximum security jail on January 9, the Metropolitan Police said.
They are being held on suspicion of conspiracy to murder and preparation of a terrorist act under Section 5 of the Terrorism Act 2006.
A prison officer suffered stab wounds to his head, chest and face during the attack, and four other members of staff suffered stab injuries as they stepped in to help.
The attackers were wearing fake suicide belts and used improvised bladed weapons, police said at the time.
The two suspects remain in custody at a London police station.
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