The government was told about a huge rise in drug use at HMP Birmingham a full two months before it was the scene of Britain's worst prison riot for nearly 30 years.
Only two days after the 12-hour rampage at the prison of more than 600 inmates, it has emerged that a report had been published on 27 October which found drugs were prevalent in all wings of the jail and had, in fact, increased since April 2016, when psychoactive substances had been made illegal.
These included "spice" and "black mamba" and, together with a rise in bullying and intimidation, meant that officers were struggling to handle a volatile environment.
"Many staff are now concerned for their personal safety as well as for the safety of the prisoners and how to deal with the next 'mamba attack'. A solution is required urgently," the report by the independent monitoring board found, according to The Guardian.
Mike Rolfe, chairman of the Prison Officers' Association, predicted there would be more such disturbances in the coming weeks and months, and warned of a prison service in meltdown.
"We're seriously concerned about the state of prisons, not just with the high levels of violence, but the now regular theme of rioting, which is spreading," he said.
Nick Hardwick, chairman of the Parole Board, told BBC Radio 4 that government plans to recruit 2,500 prison staff would not be sufficient to secure the prison service, and that prison numbers needed to go down to stop jail riots in future.
"The levels of violence, and suicide, and self-harm are not merely increasing, but the rate at which they are increasing is accelerating. We have now had a succession of very serious incidents, and the fact that you now have this spate of them is a matter for the most serious concern," he said.
After the riot on Friday, said to be the worst since the Strangeways riot in Manchester in 1990, about 240 prisoners from Birmingham were transferred to other prisons over the weekend. Fifteen of them went to Hull Prison, where inmates torched CCTV cameras and assaulted staff in protest.
There are fears that Hull could be scene of the next prison riot. Rob Nicholson, the Hull chairman of the Prison Officers' Association, told the Hull Daily Mail: "It is a powder keg and it's waiting to go off. They are trying to incite riots here and we've had a really bad couple of days."
Liz Truss, the justice secretary, is due to make a statement about the Birmingham riot on Monday (19 December).