The day I learned how to confront street crime

But Metropolitan Police Commander Mark Simmons backed up Brown's tough stance, telling the crowd: "We have arrested over 3,000 people ... we will be absolutely relentless in our pursuit of people who use knives."

My hunch is that the marchers know that this punitive message is also a divisive one. So what do you do when you see the violent or antisocial behaviour on London's streets? Do you wade in and punish — or do you try to effect a genuine resolution of conflict? I believe that it's up to all of us to step up when we see people getting out of hand, but until recently my interventions have been conspicuously unsuccessful.

On one occasion, I accosted two (black) lads jemmying a parking machine, only to have them pursue me shouting abuse. My instructions to (black and white) teenagers to pick up the litter they've discarded have almost always ended in angry confrontations. When I've tried to break up interracial fights, the combatants have turned on me.

Then a close friend who's also an inveterate interventionist pointed out to me that I tend to be angry myself when trying to stop the social rot, and so the next time I saw a (white) man about to beat up a (black) traffic warden, a couple of weeks ago, I approached them with almost Zen-like calm. I discovered that if I was firm, refused to act as arbiter, but merely told them the facts — nothing would be solved by violence — that I actually succeeded in preventing a stupid wrangle ending up as a serious assault. I was so excited by this that I then told a gang of (black) Kennington youths to pick up their litter — and they did!

This experience did teach me a key lesson about law and order: it must be enforced by individuals who are perceived as non-partial and unthreatening. I've indicated the ethnicity of all involved in these conflicts, because the fact is that in areas with high ethnic minority populations — such as those most affected by knife crime — the Met is still not policing with general consent. Despite all the work done since the Macpherson Report, black and brown Londoners continue to perceive the police as racist, while there still aren't proportionate numbers of black and brown police officers.

You would think that Commander Simmons would understand this only too well, given the current brouhaha about racism in the Met's highest echelons, but then it isn't him who's charged with actual conflict resolution on the ground. If the scourge of knife crime is to be tackled, it needs a citizenry and a police force who can intervene effectively when they see low-level antisocial behaviour on London's streets.