Video report by ITV News National Editor Allegra Stratton
It’s come to something when pupils are taken out of school to search the local estate for weapons, but the latest crime stats show why the authorities now think this necessary.
Today's figures show knife crime has increased again, by 7%, to a record high.
The police need children to be involved and alert.
We went on just such a weapons sweep on Wednesday with London's Metropolitan Police Commissioner, Cressida Dick.
Today’s figures contain good and bad news for her and other commissioners around the country.
There's the depressing continued rise in knife crime; but there's also better news - a fall in the number of murders involving a knife in the months up to June.
As usual, it's a complicated story.
These figures are for a period up until June of this year.
They reflect the mood coming out of police forces before the summer.
The Met Commissioner then was saying she believed violent crime was stabilising.
Back then the government was encouraging the police to use section 60s - a time limited period where they could stop anybody within a certain geographical area and search them without a clear reason.
It appears these section 60s had a partial effect on the number of murders involving a knife (though campaigners believe their use also damages community relations).
But, when looking at the murder numbers, whatever worked in London up until the beginning of the summer shows dangerous signs of unwinding.
While the Met is pleased to say fewer under-25s have been killed this year, more broadly the picture is worrying.
Up until this time in 2018, 110 people had been murdered in the capital.
Now, so far in 2019, it has been 117.
If things continue at this pace, this year in London will be the most deadly for a decade.
We put this to Cressida Dick on Wednesday and she acknowledged the headline numbers were going in the wrong direction: "It's horrible that homicides are higher than last year."
She told us her force had had its successes - the number of young people stabbed in London is down by about 15% on the previous year - 300 fewer young people stabbed than 12 months ago: "That's a good achievement because it was going up and up and up previously."
This morning we spoke to the family of one of those murdered this year - 18-year-old Cheyon Evans.
He was stabbed just once in the chest in June.
His mother Sarah told me that the day he died she remembered him in her kitchen cleaning up for her, as he liked to do, and singing.
Sarah and Cheyon's sister told us that young people in their local area feel in great danger and carry knives for their protection.
What will also happen is young people will share weapons, and rather than keep them on their person, they will hide them in bushes and climbing frames in communal spaces for communal use.
Which is why the Met Commissioner and London mayor Sadiq Khan on Wednesday joined school children searching for weapons in Camden.
The MET Commissioner was, perhaps unsurprisingly, particularly meticulous in her searching of the play area.
She advised the school kids to look closely at the joists underneath wooden climbing frames as that was where people often chose to hide their weapons.
In the end Cressida Dick found the only weapon - a pair of sharp scissors stuck in the ground, quite clearly left ready for someone to grab if they needed to.