A prisoner has been murdered at Wandsworth Prison. Officers were called to the jail in south London at 7.35am on Bank Holiday Monday.
The victim is believed to be aged in his 60s and though next of kin have been informed, formal identification has not yet taken place.
A man in his 40s, also a prisoner, has been arrested on suspicion of murder. He is currently in police custody.
Wandsworth, a category B prison, is the largest in the UK, and can hold more than 1,800 prisoners. It is one of the biggest prisons in Western Europe.