Are prisons becoming more dangerous places?
One prisoner has died and two others have been critically injured at HMP Pentonville - the third killing in England and Wales jails since the start of 2016. How dangerous are our prisons?
How many assaults were there?
Violence in prisons is on the rise, with assaults by inmates on each other and on staff increasing year on year.
There were 22,195 assaults across all prisons in England and Wales between March 2015 and March 2016.
This was the sharpest rise in the past decade, an increase of over 31% in one year.
Rise in assaults in prisons
All assaults, England and Wales
The prison population as at the end of March 2016 was just over 85,400, which was a slight drop on the same month the year before.
However, the rate of assaults has still increased.
The figure for 2015-16 was equivalent to 260 for every 1,000 prisoners. This compared with 198 in 2014-15.
The Chief Inspector of Prisons, Peter Clarke, has warned that prisons had become "unacceptably violent and dangerous places".
How many people have died in prison?
Over the same period, there were 321 deaths in prison custody. This is the highest figure for 10 years and 74 more than the previous year.
It works out at 3.8 deaths per 1,000 prisoners.
Five of the deaths were homicides, down from 7 the year before.
Most deaths, 186, were put down to "natural causes" and 105 were "self-inflicted".
Where do most assaults happen?
The highest rate of assaults occurred at HM Young Offenders Institution Werrington, in Staffordshire.
In 2015, there were 360 assaults. The institution has a capacity of 142, meaning two or three assaults recorded for every inmate space.
Prisons and YOIs with highest assault rates
Assaults per 10 prison places
What's the situation in Pentonville?
HMP Pentonville, a Category B prison, recorded 50 serious assaults in 2015, a big rise on the year before.
However, the overall number of assaults was down. There were 421 assaults in 2015, 74 fewer than in 2014.
HMP Pentonville assaults 421 Total assaults in 201536 "serious" prisoner assaults 7 more than the year before 14 "serious" staff assaults 8 more than the year before Source: MOJ
Assaults on prison staff were also down, but the number of serious assaults increased by 8.
No prison officers are understood to have been injured in the latest incident.
Total assaults in 2015
36 "serious" prisoner assaults
7 more than the year before
14 "serious" staff assaults
8 more than the year before
How are prison staff elsewhere affected?
Assaults on staff in English and Welsh prisons were up 40% as well, with 5,423 incidents, compared with 3,887 the year before.
Assaults on prison staff
assaults in 2015-16
more than the year before
626 serious assaults on staff
63 assaults on staff for every 1,000 prisoners
17 more assaults per 1,000 prisoners than the year before
What's being done about prison violence?
The Ministry of Justice says it will recruit an additional 400 prison officers, investing an additional £14m in 10 of the "most challenging" prisons.
"The Secretary of State has been clear that safety in prisons is fundamental to the proper functioning of our justice system and a vital part of our reform plans," said a spokesperson.
"We are fully committed to addressing the significant increase in violence, self-harm and self-inflicted deaths in our prisons.
"Earlier this month the Justice Secretary announced an immediate investment of an additional £14m in ten of our most challenging prisons, increasing staffing levels by over 400 prison officers.
"In the coming weeks she will be publishing a White Paper setting out plans across the estate for prison safety and reform to 2020 and beyond."