A murder investigation has been launched into the death of an inmate who was attacked at a high-security prison.
The 36-year-old prisoner was found with head injuries at HMP Belmarsh, south-east London, at 20:00 GMT on Tuesday, Scotland Yard said.
He was taken to hospital in a critical condition but died on Wednesday night.
Two 28-year-old inmates were arrested on Tuesday evening on suspicion of attempted murder.
Det Ch Insp Richard Leonard said: "At this stage I am open minded concerning motive, but expect this to become clear as the investigation progresses."
The Met is working to establish the circumstances surrounding the death with local prison staff.
A post-mortem examination will take place in due course.
HMP Belmarsh is one of only three high-security core prisons in England and Wales.
A 2018 inspection report showed that levels of violence had increased at Belmarsh since a previous inspection in 2015.
The jail opened in 1991 and is able to hold 910 prisoners, according to the Ministry of Justice.