Over the bank holiday weekend, a spate of shootings across England hit the headlines. They add to a picture of rising gun crime, after more than a decade of big decreases.

Although gun-related offences have risen for the past four years, there were still less than half as many gun crimes in England and Wales last year as there were in the early 2000s.

Where do the guns come from?

Guns are very tightly controlled in the UK. Those that end up on the black market often start off as legal guns - but become illegal because they are modified or their licence status changes.

For example, a legal gun covered by a firearms licence could be stolen from a farm or firearms dealer.

Murdered MP Jo Cox was killed with a gun that had been stolen from someone who held it legally with a licence.

Also, non-firing ceremonial guns or race-starting pistols can be modified to fire bullets.

And decommissioned guns used in conflict can be reactivated - especially because the standards of "deactivation" vary around Europe and in some cases the process is very easy to reverse.

In 2017, Europol - the EU police agency - said: "The reactivation of deactivated weapons and conversion of blank-firing firearms are among the main sources of illegal firearms trafficked in the EU."

The National Crime Agency (NCA) in the UK says blank-firing and deactivated guns are bought legally by organised crime gangs in Europe who then "reactivate" them - often by removing an obstruction from the barrel - and sell them in the criminal market.

Some of these then end up in the UK, often coming from Eastern Europe, hidden in heavy goods vehicles, by sea or even in the post.

Guns or parts of guns are also traded online. In 2015, NCA officers seized a gun that had been sent to a man in the UK in the post, concealed within a radio.

And finally, there is a growing problem in the UK of antique guns that use obsolete kinds of ammunition being fitted with home-made bullets.

Image caption Guns such as this Russian made Baikal pistol were built to fire CS gas canisters and can be adapted to fire live 9mm ammunition

The problem with antiques

The National Ballistics Intelligence Service (NABIS) said that it was identifying more cases where home-made ammunition was used, nodding to a rise in the use of antique weapons by criminals.

"One of the trends which emerged over recent years is offenders increasingly using obsolete calibre or 'antique' firearms, which are easier to get hold of," it said.

In one high-profile case, Paul Edmunds, a registered firearms dealer, was jailed for making ammunition to fit antique guns, which he then sold to criminal gangs. His guns were linked to about 50 crime scenes.

NABIS manages the national database for all recovered firearms and ballistic material, including bullets and cases.

It runs forensic labs and works with police forces in England, Wales and Scotland to link this recovered ballistic material to guns, where no gun is recovered at a crime scene, and to crimes.

In 2015-16, 30% of the guns used in crime that the organisation recovered and tested were "obsolete calibre", meaning they were designed for ammunition no longer produced - in other words, antiques that have been repurposed to be used in crime. This represents a significant rise over the past five years.

The rise in the use of antique weapons is thought to be a sign that non-antique guns have become more difficult to obtain.

Gavin Hales, a former deputy director of think tank the Police Foundation says the fact that individual guns are found to have been used in crimes committed by different individuals suggests that the number of illegal firearms in circulation is likely to be quite small.

"Evidence of particular guns popping up all over the country tells us something about how hard it is to get hold of them," he says, adding that high prices mean criminal guns often get sold on rather than being destroyed after being used.

However, it also serves as an indication of how much damage just a small number of guns in circulation can do.

What types of guns are being used?

Handguns were the most common type of firearm used to commit offences last year, according to police records.

Some of these will also be converted guns, for example Baikal handguns designed to fire gas canisters are modified to turn them into lethal weapons.

They are followed by "imitation weapons". This category, which includes antiques and blank-firing guns that have been converted to fire bullets, has grown the most over the past 10 years.

Dr Helen Poole, an expert in firearms crime, at the University of Northampton, says evidence from Europe that far more firearms are recorded as stolen than are seized suggests an increasing number in circulation.

How common are these crimes?

Gun crime remains rare in Britain.

In England and Wales in 2016-17, there were 31 fatal shootings - or one for every 1.9 million people.

And there were 9,578 weapons offences that resulted in injury.

In the US, in contrast, there were 11,000 murders or manslaughters involving a firearm or one death for every 30,000 people.

There are particular hotspots in the police force areas that cover large urban centres.

London had the most firearms offences per head of population, followed by the West Midlands force area, covering Birmingham, West Yorkshire, covering Leeds, and South Yorkshire, serving Sheffield.

Last year:

just over half of all firearms offences involved a gun actually being fired

in just under half of cases, a gun was used as a threat

in a small minority of cases, a gun was used as a blunt instrument

There is evidence of a genuine rise in crime - NHS figures reveal an increase in hospital admissions in England for assault by firearm discharge.

But part of the increase in recorded offences could also be down to the police prioritising gun crime. As they focus more of their efforts on looking for these crimes, they find more.

Read more from Reality Check

Send us your questions

Follow us on Twitter