British prisons: Five major incidents in 12 months
Details of the five major incidents reported in British jails over the past year, as unrest is reported at HMP Swaleside.
Unrest at HMP Swaleside on the Isle of Sheppey in Kent is the latest violent incident in British prisons.
Here are some of the incidents reported in the past 12 months.
December 16 - HMP Birmingham Hundreds of prisoners rioted, setting fires, stealing keys and trashing some areas over 12 hours. Prisoners tweeted photographs of themselves wearing guards' helmets and dangling bunches of keys.
Tales from jail: Why UK prisoners are rioting and why there will be more
After more prison unrest, three ex-inmates talk to Sky News about their experiences with drugs, drones and violence.
By Becky Johnson, North of England Correspondent
A week on from the worst prison riot in a quarter of a century, the damage caused by hundreds of rampaging inmates at HMP Birmingham is still being repaired.
Images of the riot filmed on mobile phones illegally smuggled into the prison may have shocked some, but former inmates from across the country have told Sky News the unrest came as no surprise to them.
Painting a grim picture of prisons where drug-fuelled violence is part of everyday life, three young men told us their experiences and why they think we will see the scenes in Birmingham repeated in other jails.
Javed Ali was convicted of blackmail and sentenced to two-and-a-half years in prison. He spent time in jails across the north of England until his release in July.
"Five times a day you used to get the general alarm go off," he says. "People being stabbed, broken jaws, broken limbs, cuts to the neck.
"It's very easy to get hold of drugs in prison. It's a lot easier than it is to get hold of drugs on the outside."
He described how they get in: "Mostly via drones and throw-overs, which means people on the other side of the fence or the other side of the wall throw over the parcels of drugs, alcohol, weapons and phones.
"Prison officers, some of them do a really good job, but most of them have sort of given up. There's only so much that they can do.
"They see a person having a spice attack, which is a bit of an attack when you're taking drugs, and they just close the door; they put them in a corner because it's a lot of paperwork, it's a lot of hassle and they don't have a lot of manpower for it."
"There's a massive issue with drugs and boredom," Javed adds.
"The prisons have to go into lockdown because they're understaffed, and not just because there's an incident - most of the time they're just understaffed."
Jack Wilcock served 14 months for armed robbery and says long hours spent in cells fuels aggression. He kept a diary during his time inside. On one occasion he documented witnessing two fights before 7.30am.
"I think that's one of the main driving factors of riots. It's boredom, frustration and a bit of rebellion going on at the same time," he says.
"I wasn't surprised at all about the Birmingham riot. These type of things happen all the time to a much lesser extent, prisoners get riled up in big groups and start acting violently. They start acting with one aim, one goal, and it's against the system.
"If nothing changes and it just keeps going in the same direction, you'll probably see more prison riots."
Danny Wilcock has spent eight of his 32 years behind bars.
"I've been waiting for it to go off across the prison establishment, across the country, for a couple of years now, it's inevitable," Danny told Sky News.
"They've just literally got enough staff to lock the doors and get you out for your dinner. If something kicks off, 200 all angry want to kick off - they will bring the prison down."
A Ministry of Justice spokesperson said: "We have announced a major shake-up of the prison system with 2,500 extra prisons officers and new security measures to tackle drones, phones and drugs, and help make prisons places of safety and reform.
"The Justice Secretary has always been clear that it will take time to address these long-standing problems and we must grip the real challenges and risks that we face in the shorter term.
"That is why we have taken action and set up a new prisons task force to manage down potential flashpoints of unrest in prisons, as well as a new £3m national intelligence hub to target gang crime behind bars."
Rob Nicholson, chairman of the union's Hull branch, told the Hull Daily Mail: "They are trying to incite riots here and we've had a really bad couple of days here."
Mike Rolfe, national chairman of the POA, said he was aware of "some simmering tensions" across a number of jails.
Parole Board chairman Nick Hardwick said plans to recruit a further 2,500 prison staff did not go far enough to prevent violence.
Mr Hardwick, an ex-chief inspector of prisons, added: "It would be a mistake to take emergency, reckless measures around the prison population, but if you don't do things in a planned and sensible way, then further down the track they may be forced into a much more difficult position."