Jimmy Mizen was killed in a south-east London bakery in May 2008
The Prince of Wales was among the guests at a service for victims of violent crime organised by the family of murdered teenager Jimmy Mizen.
The Building A Legacy of Peace event at Westminster Cathedral marked the second anniversary of the 16-year-old's death in a London bakery.
Ahead of the service, Jimmy Mizen's parents called on political leaders to tackle violence on Britain's streets.
It came after a week which saw two teenagers murdered in the capital.
Speaking at the launch of a personal safety film for schools, Barry and Margaret Mizen said more must be done to stop young people being killed in violent attacks.
Mrs Mizen, 57, said: "The three party leaders, please all of you work together on this issue.
"We keep working for peace around the world but we have no peace on our streets. Sometimes I feel it's like it's a war out there on the streets of our beautiful country."
Peace service for murder victims
The film, produced by not-for-profit organisation Kids Taskforce in memory of Jimmy, will be distributed to all secondary schools in England and Wales.
The Jimmy Mizen Foundation charity, set up after his death, said the Building A Legacy of Peace was a national call for peace.
Jimmy bled to death the day after his birthday when Jake Fahri, 19, threw a glass tray at him in the Three Cooks bakery in south east London, severing an artery in his neck.
Fahri, from Lee, where his victim also lived, was given a life sentence for the murder in 2009.
Since the killing Jimmy's parents have tirelessly campaigned against violent crime.
Mrs Mizen told the BBC: "Obviously the service is for me to remember my son - it was his 18th birthday yesterday.
"But it is also about everyone else who has been killed."
She continued: "We want this to be an ongoing thing - I don't want any other mothers suffering as I have suffered."
They created the Jimmy Mizen Foundation which funded two "Jimmybuses" for local scout groups.
The service was the second commemorative event arranged by the family.
Among the invited guests were families of other victims, including 10-year-old stabbing victim Damilola Taylor and young actor Robert Knox, who was killed outside a bar in south-east London.
Barry and Margaret Mizen have become anti-knife crime campaigners
Representatives from the police, social services and education departments also attended.
Recent BBC research found a 30% decrease in the number of teenagers murdered across the UK.
In 2008, 72 people aged between 10 and 19 were murdered, while 51 died in 2009.
To date, 11 teenagers have been murdered in London in 2010, and eight of those have died in the last six weeks.
Last Wednesday, Nicholas Pearton, 16, died in his mother's arms after being stabbed and beaten as he tried to flee from up to 10 attackers in Sydenham, south London.
Another teenager, a 19-year-old man, was stabbed to death near Finsbury Park Tube station in north London on Saturday night.