A prisoner has died after his throat was slashed inside a privately run jail in southeast London.
Scotland Yard said the man, who was in his 40s, was attacked at HMP Thameside in Greenwich in the early hours of Sunday.
He was discovered suffering a slash injury to his throat and died at the Serco-run facility, which opened in 2012 and holds around 1,200 inmates.
A man in his late 30s has been arrested on suspicion of murder, police said.
A spokesman said: “Police were called at 02:37hrs on Sunday, 12 January to HMP Thameside in Greenwich after an inmate was discovered suffering from a slash injury to his throat.
“The man, aged in his 40s, was pronounced dead at the scene by London Ambulance Service.
“Officers are working to inform his next of kin.”
Formal identification and a post-mortem will take place in due course.
Officers from the Specialist Crime Command have been informed and enquiries are continuing into the circumstances.
HMP Thameside serves courts in east and southeast London and has an “extremely high turnover of prisoners” with the average stay a “mere 36 days”, according to an inspection report in 2017.
The prison had a “generally settled and respectful atmosphere”, HM Chief Inspector of Prisons Peter Clarke said, but he noted that “levels of violence were high”.
He added: “However, there was a good violence reduction plan in place and although there had not been a reduction in violence, Thameside had bucked the trend in comparable prisons as it had not experienced the huge rises in violence seen elsewhere. This was a significant achievement.”