Four young British Muslim extremists chanted religious slogans as they battered a prison officer.
The gang chanted "death to the Kuffar" (non-believer) and "Allah Akbar" (God is Great) as they laid into the warder - who is in his 40s - after prayers.
It is believed they were trying to steal his keys to let other inmates out and start a riot at the notorious Feltham Young Offenders' Institute in Middlex.
A fellow officer came to his rescue as he hid under a pool table and used his baton to drive them back....
A source said: “It was a frightening and violent assault. The guard was lucky to escape with his life.”