Riot police were called to Broadmoor Hospital today after patients went on the rampage, smashing up furniture and doors and destroying security cameras.
For almost four hours staff at the top-security hospital, which houses killers, arsonists and rapists, were held at bay by the rioters.
A squad of 20 riot police were at the scene, along with paramedics and firefighters after the alarm was raised by night duty staff at the all-male psychiatric hospital.
Off-duty nurses were called back into the hospital in Crowthorne, Berkshire, after the disturbance broke out shortly before 12.30am.
Sources said that the ward involved held 15 male patients and the rioting began after four of them initially embarked on a rampage.
Unconfirmed reports suggested that eight or nine patients broke out of the ward and were on the loose in the hospital.
“Four of the ringleaders set about smashing up the ward and broke security cameras which were housed in the ceiling as well as damaging walls, doors and furniture,” said a source.
“It had all the potential to turn into a full-scale riot,” added the source.
A spokesman for the West London Mental Health Trust said: “In the early hours of this morning there was a disturbance on a ward at Broadmoor Hospital involving four patients.
“I can confirm that a full-scale internal inquiry into the incident has been launched.”