Relatives of a teenager stabbed to death in London last year have backed a campaign to clampdown on knife crime.
Police will use metal detectors in hotspots
Pat Levy said the fatal stabbing of her 16-year-old son Robert, who was trying to protect another boy from attack, had left the family "devastated".
Metropolitan Police in all 32 London boroughs will be targeting those who carry and use knives as part of Operation Blunt.
Some 80 people were killed in knife attacks in London last year.
For the past year the scheme has been piloted in 12 boroughs - reducing this type of crime in all but two of them, according to Scotland Yard.
"To say the family is devastated by Robert's death is an understatement," Mrs Levy said in a statement read out at the launch of the campaign.
"We are the ones who have been given a life sentence, this has changed our lives for ever."
Robert was stabbed near his home in Hackney, east London, in September 2004. His 15-year-old killer was sentenced to a minimum of nine years in jail in April.
Robert's uncle Franklyn Edwards, who attended the launch, said his nephew's death was "like a nightmare".
"The only difference being that with a nightmare you know you are going to waken, and the pain is going to ease," he said.
"Don't carry knives. If you're confronted by trouble, run away, you're not a coward if you run away."
Robbery and assault
Officers will take their message into secondary schools and target knife crime hot spots.
Territorial Policing Commander Alf Hitchcock, who heads the project, said: "Our message is clear - carrying a knife is not a game.
"The consequences don't get any more serious. If you carry a knife you are more likely to become a victim yourself."
From April 2004 to April 2005 there were more than 12,000 offences involving knives, most of which were robbery and assault.