A murder investigation has been launched after an inmate was attacked at high-security Belmarsh prison.
A 36-year-old man was found with head injuries after an assault in the jail on Tuesday night.
He was taken to hospital in a critical condition but died the following evening.
Police had been called to the prison just after 8pm on Tuesday and two inmates, both 28-year-old men, were arrested on suspicion of attempted murder.
Belmarsh is one of only three high-security local prisons in England and Wales and has housed some of Britain's most high-profile prisoners.
Julian Assange, 48, is being held on remand there ahead of his extradition hearing, while Tommy Robinson served his sentence at Belmarsh last year after being jailed for contempt of court.
Other inmates known to have been housed in the prison are Michael Adebolajo, one of the killers of soldier Lee Rigby; Finsbury Park terror attacker Darren Osborne; and radical preacher Anjem Choudary before his release from jail in 2018.
An inspection report in 2018 showed that levels of violence had increased at Belmarsh since it was last assessed three years previously.
It opened in 1991 and had an operational capacity of 910 prisoners as of 2008, according to the Ministry of Justice.