Nine charts on the rise of knife crime in England and Wales
There is nothing new about knife crime: sharp objects, blades and knives have been used as weapons for thousands of years.
But after falling for several years, knife crime in England and Wales is rising again. So what is happening?
There were 40,147 offences in the 12 months ending in March 2018, a 16% increase on the previous year and the highest number since 2011, the earliest point for which comparable data is available.
Out of the 44 police forces, 38 recorded a rise in knife crime since 2011.
Police figures are prone to changes in counting rules and methods, but data for NHS hospitals in England over a similar period showed a 7% increase in admissions for assault by a sharp object, leading the Office for National Statistics (ONS) to conclude there had been a "real change" to the downward trend in knife crime.
All of the statistics here relate to England and Wales. Policing, criminal justice and sentencing are devolved in Scotland and Northern Ireland, which also collect crime data in slightly different ways.
In the latest figures, which include only selected knife offences, about half, 18,787, were assaults that caused an injury or where there was an intent to cause serious harm; a further 17,207 involved robberies.
These figures focus on homicides, or killings, a category comprising cases of murder, manslaughter and infanticide. In about two out of every five killings, the victim is fatally assaulted with a sharp object or stabbed to death.
The proportion of homicides that are knife-related has remained broadly the same over the past decade, though the overall number is lower. Most of the victims are men. The "Other" category includes poisoning, burning, shaking, being struck by a vehicle, negligence, neglect, explosions and cases where the cause isn't known.
Although knife crime is on the increase, it should be seen in context. It's relatively unusual for a violent incident to involve a knife, and rarer still for someone to need hospital treatment.
Most violence is caused by people hitting, kicking, shoving or slapping someone, sometimes during a fight and often when they're drunk; the police figures on violence also include crimes of harassment and stalking.
The Crime Survey for England and Wales, which includes offences that aren't reported to police, indicates that overall levels of violence have fallen by 25% since 2013.
However, the police-recorded statistics - which tend to pick up more "high harm" crimes- have indicated that the most serious violent crime is increasing.
In the year to June this year, 20,113 people were cautioned, reprimanded or convicted for carrying a knife in England and Wales, most of whom were adults. But one in five, 4,291, was under the age of 18, the highest number for eight years.
Knife crime tends to be more prevalent in large cities, particularly in London.
For every 100,000 people in the capital, there were 137 knife offences in 2017-18, with separate figures, from the mayor's office, showing that young black and minority ethnic teenage boys and men were disproportionately affected, as both victims and perpetrators.
Next highest was the West Midlands, with 65 knife offences per 100,000 population, and Yorkshire and the Humber, 54.
The explanations for rising knife crime have ranged from police budget cuts, to gang violence and disputes between drug dealers.
Some have also cited the steep decline in the use by police of stop and search.
The powers enable officers to search people on the street if they have reasonable grounds to suspect they may be carrying weapons, illegal drugs, stolen property or items to be used to commit a crime. People can also be searched without reasonable grounds if a senior officer believes there's a risk of serious violence in a particular area.
From 2009, the number of stops has been falling across England and Wales, especially in London, primarily because of concerns that the measures unfairly targeted young black men, wasted police resources and were ineffective at catching criminals.
Theresa May, as home secretary, led efforts to drive down the number of stops, but there's anecdotal evidence from police that young people are now more inclined to carry knives because of growing confidence they won't be stopped.
The statistical basis for that is far from clear - but Scotland Yard and the mayor of London are now preparing to increase the use of stop and search again.
The average prison term for those jailed for carrying a knife has gone up from almost five months to well over seven months, with 81% serving at least three months, compared with 57% only 10 years ago.
Sentences for all kinds of violent crime have been getting tougher, particularly for knife crime. The Ministry of Justice tracks the penalties imposed for those caught carrying knives and other offensive weapons in England and Wales.
In the year ending June 2018, 33% were jailed and a further 16% were given a suspended prison sentence. The figures for 2008, when the data was first compiled, were 18% and 8% respectively. Over the same period, there's been a steady decline in the use of community sentences, and a sharp drop in cautions, from 34% to 15%.
Public anxiety about knife crime, legislative changes and firmer guidance for judges and magistrates have led to the stiffer sentences, although offenders under 18 are still more likely to be cautioned than locked up.