Video report by ITV News National Editor Allegra Stratton
It was one of the worst prison riots in England for 25 years.
More than 500 inmates took control of four wings at Birmingham Prison in December 2016.
It all started when a prisoner jumped on to the safety netting, a guard came to negotiate but was threatened with a syringe filled with blood, then another inmate snatched his keys to the cells.
The prison officer, who asked to remain anonymous said: "I can remember seeing hordes of prisoners running around - you could see the fear in the face from everybody.
"The potential to lose the jail was as real as it was ever going to get."
Former HMP Birmingham prisoner Courtney Hamilton described the chaos that ensued.
"Everything that can catch fire at that point, people were setting it on fire, some inmates put two mattresses through my door and lit it - I thought I was going to lose my life."
In the wake of the riot the government conducted an investigation, which it then refused to release on security grounds.
But now ITV Exposure has obtained parts of the report and the conclusions are damning.
They say that although there was sufficient staff on the day, the riot could have been prevented.
"Staff were being worn down by chronic staffing shortages over the previous year and prisoners were in effect policing themselves for much of the time."
The company that runs Birmingham prison G4S praised their staff in the face of aggression and said the prison had undergone changes since.
A government spokesperson accepted there were challenges and said they had recruited more prison officers since.
But the official report says the factors that triggered a riot in Birmingham are not unique, other prisons around the country are under considerable pressure too.
Prisons Uncovered: Out of Control will be broadcast on ITV on Monday 10th June at 10.45pm