Ealing, London // On Haven Green, normally a tranquil, leafy corner of west London, a police van screeched to halt beside me.
Seeing our family group trailing two suitcases and a two-year-old toddler, an officer poked his head out of the passenger window and practically screamed at us: "Go home now."
It was an alarming return to the UK after months in the south of France, where I mostly live and work.
And if the sense of urgency in the policeman's voice had seemed, at 10pm with no trouble in immediate sight, excessive, his concern was soon vindicated. He knew, though we did not, that a mob hundreds strong had begun a rampage only a street or two away.
Even on the short drive home in my daughter's car, a journey made longer by the need to choose a circuitous route and give the centre of Ealing a wide berth, it was clear he was not exaggerating at all.
We passed a band of marauding youths whose hooded faces and sharp, aggressive movements hardly suggested people out to take the evening air.
By daylight, the evidence was plain to see: wreckers and looters had inflicted substantial destruction in a part of the capital historically known as the "queen of suburbs".
Along one parade of shops and restaurants, windows had been kicked in, stock and furnishings trashed. Burnt-out cars littered the road leading to one of Ealing's beautiful expanses of parkland, producing a scene reminiscent of my time spent covering the Troubles in Northern Ireland, the English inner-city riots of the mid-1980s and the nationwide French disturbances of 2005.
I have been threatened in Belfast and on the Kosovo-Macedonia border, and tear-gassed in Paris, but somehow this seemed worse, perhaps because it was on home ground, far removed from places I associate with menace.
Walking along a road that leads away from Ealing centre, past the famous old Ealing film studios, I could not help but notice the random nature of the damage: a babies' clothes shop, a Chinese takeaway restaurant, a bistro, a pub, a health food shop, a mini-supermarket, a little coffee bar. When looters set fire to one store, people in the flats above had to flee for their lives.
The traders were angry. Liz Pilgrim, owner of the baby boutique, wanted David Cameron's government to order troops on to the streets to combat the mobs. A hairdresser with a salon on the fringe of the affected area said: "It won't happen, but the only sure way to stop it would be to shoot a few of them."
Nearer Ealing Broadway underground station, which had been closed on police instructions shortly after our uneventful arrival, more shops had been attacked.
About 40 small businesses were targeted and in almost each case, rioters - including boys and girls in their early teenagers, according to some witnesses - had gone for the cash tills.
Nor did the houses and flats of the residential area surrounding Ealing centre escape unscathed.
Jo-Ann Scott described on Sky News the horror of turning on her bedroom light at 11.30pm and finding someone - man or woman, she could not tell - dressed all in black standing over her. "I just asked 'What do you want?'," she said. The intruder turned to an accomplice, said "let's get out of here", and both left.
Ealing was not, of course, an isolated trouble spot. Television and newspaper images bore witness to the devastation suffered by businesses in other London areas - Croydon, Enfield, Clapham and Woolwich among them - and to astonishing levels of lawlessness, rioters bombarding police with missiles but also, in some cases, willing to engage in hand-to-hand combat. Many of the participants were black, but the footage captured numerous white faces, too.
It was the third night of violence since the first disorder of Saturday night, ostensibly a reaction in the north London district of Tottenham to the fatal shooting by police of Mark Duggan, a suspected armed criminal, two days earlier.
But Monday's rioting began in broad daylight, in the east London area of Hackney, and quickly spread as overstretched police and fire services struggled to cope with each new outbreak.
Whatever questions arise over the conduct of police in their attempt to arrest Mr Duggan, the nature of the subsequent violence suggests straightforward criminal opportunism with gangs making the most of the chaos to rob shops, especially those stocking electronic goods, designer clothing, jewellery and sportswear.
Inevitably, the media coverage and extensive use of social networks - notably Twitter - led to what one police spokesman called "copycat criminality" in the cities of Bristol, Liverpool, Nottingham and Birmingham.
Sky News even interviewed a man who spent years in prison for his part in the Bristol riots of the 1980s - sparked by accusation of police heavy-handedness towards the black community - but accuses the rioters of 2011 of being motivated by "thuggery, not idealism". Chris Sims, chief constable of the police force covering Birmingham, said of events in his city "This was not an angry crowd, but a greedy crowd."
But as attention turned nervously to the nights ahead, no one could say with any certainty where trouble would next erupt, and when it would end.