And it would seem that they have all been murdered by other young men carrying knives.
Tuesday's demonstration was all the more poignant because it was organised by Ben's friends. It had a clear message which echoed the challenge coming from the family "Put down your knives".
The minority of young people who believe that knives make them safer, bigger and cooler must take heed of this message.
We should have a knife amnesty; youngsters should have a chance to get rid of their weapons voluntarily.
But if they don't, those who are caught carrying them are likely to go prison and those who use them will be caught and spend most of their lives in prison.
I am reassured to hear that the number of police officers searching teenagers for weapons has greatly increased recently. There are up to 50 officers stopping youngsters at all hours on Islington's streets.
I had a private meeting with Ben's mum on Monday night, and I agree with her that no mother should go through what she is suffering, ever again.
Islington's teenagers need to put down their knives.
