If there is one thing that prison officers and inmates agree on, it is that in prison drugs and violence are inseparable. And there are many people who believe the country's prisons are awash with drugs.
Many say drugs are readily available in prisons
The situation in one prison was revealed on Tuesday, when Gordon Hacker, a former prison officer at HMP Rye Hill in Warwickshire, was sentenced to four years for conspiring with inmates to smuggle in drugs.
He tipped off inmates about the best times for drugs to be thrown over the perimeter wall, and in doing so helped supply prisoners with heroin, ecstasy and cannabis.
It is not the first time problems have been exposed at Rye Hill. In April a separate Panorama investigation showed inmates attempting to groom an undercover reporter to become a smuggler, prison officers discussing being left in pairs to deal with about 80 inmates, and a female officer being openly threatened by an inmate.
'String of attacks'
But it is the prisoners themselves who are most at risk.
Over one six-month period, a former female prison officer at Rye Hill, who wished to remain anonymous, saw the aftermath of a string of threats and brutal attacks, most of which she says were drug-related.
She saw one man so terrified by a threat he would have his eyes stabbed out by a dealer, that he climbed onto the prison roof to retrieve drugs thrown over the prison wall.
She said: "He knew the consequences of what he was going to do, and he was out in a month's time. He got put on segregation and he had time put on his sentence."
Another inmate was found lying on the floor of his unit with his lip hanging off, and one inmate was beaten by a sock filled with cans of tuna.
"I didn't even recognise him," she said.
High drug use
The list goes on. Last Christmas she said an inmate almost died after having his throat cut open, and in yet another incident, she walked into a cell to find a prisoner hiding under the bed, refusing to go back to his own cell for fear of being stabbed over a drug debt on the way there.
She said: "You are supposed to be looking after them. I personally would never want to be a prisoner in there because if something is going to happen to you, it's going to happen."
Rye Hill is not unique. A 2005 Home Office report into drugs in six local prisons estimated that between 30% and 60% of inmates were using heroin, and that "the majority of prisoner/ex-prisoner interviewees agreed with the statement that the trade in drugs is the major cause of violence between prisoners".
Earlier this month, the independent monitoring board for Wandsworth prison in London, the biggest in Britain, reported that "the continuing trafficking of drugs and mobile telephones in the prison
exacerbates the problem of bullying, and threatens the safety and well being of prisoners".
"I imagine every prison has some element of drug dealing going on in it. I can't imagine any institution would be free of it," said Paul Turnbull, co-author of the Home Office report.
The report lists numerous ways inmates manage to smuggle in drugs. They include those wrapped in condoms by new arrivals and hidden internally, those smuggled by visitors and prison officers, and
consignments thrown over the perimeter wall by friends on the outside - sometimes in a hollowed-out tennis ball.
The prison population is now at record levels, and has risen over the past 10 years by about 30%. But during the same period, prisoner on prisoner assaults have rocketed from 2,441 in 1997, to 11,520 in 2007 - a rise of nearly 500%.
Tom Robson is an executive with the Prison Officers' Association representing the north west of England, and has been in the service for 31 years.
Mr Robson believes drugs are easier to get into prison than ever before, and he says it is drugs that have had the biggest impact on prison violence.
Drugs have been thrown into prisons over walls inside tennis balls
He said: "There are the vulnerable and there are those that rise to the top. At the moment we are so overcrowded and prison officers are so thin on the ground, that the policing of the situation becomes very difficult.
"The consequences are dire, and that is why we have prison officers assaulted on a daily basis, and prisoner-on-prisoner assaults are going through the roof.
"We simply have not got time to talk to prisoners...you see a prisoner sat in his cell in tears and all it takes is five or 10 minutes to sit with the prisoner and see what's wrong, and that five or 10 minutes
has been taken away."
A Ministry of Justice spokeswoman acknowledged the challenges faced by prison officers, but emphasised that the safety of both staff and inmates was taken very seriously.
She said a raft of measures were used to control the supply of drugs in prisons, including searches, drug dogs, phone detectors and CCTV, and that since 1996, drug testing results "indicate that drug use in prisons has fallen by 64%".
But according to Iain Smith, 25, who has been in and out of prisons across the north of the country since he was 18, largely for stealing to fund a heroin addiction, on the inside drugs are never very far away.
He said: "It is literally just like going next door to the next cell."
Iain has not been in prison since February, and he now advises the crime reduction charity Nacro which helped him kick his habit, but he has vivid memories of what it was like as an addict in prison.
He described the routine intimidation meted out to any new inmate thought to be carrying drugs.
As the new arrivals come in, the other inmates size them up and pick out someone who looks vulnerable.
Iain said: "The new prisoners, as they go to their cells to set up their bed, that's when you see eight or 10 guys go into their cell.
"I feel for them. They are scared, and then the next thing you know you've got 10 guys coming into your cell."
Then, he said, the other inmates force the new arrival to hand over any drugs they might be carrying.
In 2004 at HMP Nottingham, he said intimidation drove his cell mate to attempt suicide on his first night inside.
Iain said the other inmates "were basically telling him that you've got to have drugs, and he got so down, and in the middle of the night he decided to hang himself.
"I had to jump up and hold him up...and I grabbed his legs just to hold the weight off his shoelaces, and when they brought him down the shoelaces had cut an inch into his neck."
His cell mate spent the rest of his sentence on suicide watch.