A spokesperson for Serco, which runs the facility, said a prisoner was assaulted by another inmate earlier today.

“Our staff acted immediately to protect the victim and restrain the assailant.

“Hato Hone St John was called immediately, and the prisoner was transferred to hospital in a stable condition. The incident was also reported to the police, who attended the site.”

Assaults in prison are illegal, unacceptable and would not be tolerated, the spokesperson said.

“Any perpetrators should expect to face criminal charges as well as prison disciplinary processes. All incidents are reported to the police.”

Police said inquiries were under way into how the prisoner was injured.

“At this early stage of our inquiries, there is no further information available.”

Sign up to The Daily H, a free newsletter curated by our editors and delivered straight to your inbox every weekday.