A text message went from phone to phone on Sunday afternoon, inviting “all the brehs in north” to rally at Enfield station at 4pm. “Whatever ends your from put your ballys on link up and cause havoc, just rob everything,” it read. A community leader sent it on to me, and also to the police.

Then on Twitter on Tuesday, a flurry of spontaneous cleaning parties formed, fixing rendezvous and reminding each other to “bring gloves, sacks, brooms and brushes”. So this is the social upshot of the riots. The youth – the brehs – lay aside their turf wars, and coalesce; and the middle classes, so snooty about it before, suddenly form the Big Society.

It is possible to be facile (the tweet of the week, from Monday night: “all quiet in Primrose Hill, though I did see two reflexologists tut at each other outside the patisserie”). But in exposing the depths for a moment, a convulsion like this brings some sharp realisations about London in 2011. First, it shows you cannot love and spend your way to civil peace. Ken Livingstone and Polly Toynbee, tribunes of the old left, have been blaming the riots on “the cuts”, which have not even properly hit yet. The young people at the social project I run have been in “youth work” programmes all their lives; every one, to a boy and girl, will surely have been out and about these past few nights, whether as spectators or participants. In their shoes, wouldn’t you be?

The only way to stop them – the good kids and the bad – is to frighten them home with the real threat of reciprocal violence. Tim Montgomerie of conservativehome.com, the unofficial leader of the Tory grassroots, called on the police to “baton charge the yobs: without fear of the police there can be no order”. He is right.

David Cameron, announcing the near-tripling of the police presence on Tuesday, has firmly asserted the primacy of the law. (It is a side issue for now, but this episode confirms the case for elected police chiefs – the police hate political oversight but they derive their authority from it, especially in times of crisis.)

The second realisation is that the gulf between these two groups – the rioters and the cleaners-up – has been papered over by prosperity, but has actually widened as incomes rose. We have a generation of young people reared on cheap luxuries, especially clothes and technology, but further than ever from the sort of wealth that makes them adults. A career, a home of your own – the things that can be ruined by riots – are out of sight. Reared on a diet of Haribo, who is surprised when they ransack the sweetshop?

And yet even our most self-serving actions can be justified to ourselves. “I’m taking my taxes back,” said one woman carrying a TV out of a shop. Less ridiculous but no less wrong, the youth throwing bins at the police imagine they are fighting for justice. A narrative of unfairness has taken hold, and this is its expression.

The districts that took the brunt of the rioting on Monday night were not sink estates. Enfield, Ealing, Croydon, Clapham ... these places have Tory MPs, for goodness’ sake. A mob attacked the Ledbury, the best restaurant in Notting Hill.

It is people in places like these who wrinkled their noses when, in opposition, Mr Cameron talked of “broken Britain”. They felt safe in the city, and thought it ill-mannered to talk like that about the locals. Britain has got better, richer, more “tolerant” – but only, we now find, insofar that “we” are more tolerant of “them”: the esteem was not reciprocated.

The intifada of the underclass, as someone called it on Monday night, bears a pathetic comparison with the uprisings elsewhere around the Arab world during this year. Young people in Egypt and Tunisia had something to lose from their protests – their lives – and something to gain – democracy and justice. Our young people have nothing to lose and nothing to gain, except thrills and new trainers. They are simply confirming, in the most disgraceful terms possible, their own disgrace. As another friend tweeted: “these kids are telling their life stories”.

Outside 10 Downing Street on Tuesday, the prime minister spoke mainly to the rest of us, stating his resolution to restore order. He had only one thing to say to the young rioters themselves – they are in danger of wrecking their own lives by involvement in the violence.

It is true, but it does not matter. They think their lives are wrecked anyway, and a couple of months in prison (which, for all the bluster, is the likely fate of only a tiny minority of rioters anyway) will not make a difference. Inured to cheap goods, they are also inured to punishment and the threat of it.

London has an underclass (a hateful word to the people in it, but no worse, and more accurate, than “the poor”). To generalise brutally, they are un-nurtured, brought up in a microculture of neglect, arbitrary and erratic discipline, and love without its concomitant need for boundaries and good behaviour.

Meanwhile the wider culture – that is us – has abandoned virtue and adopted the ethics of indifference, dressed as liberalism. We have substituted welfare payments for relationships, rights for love, and the sterile processes of the public sector for the warm morality of living communities. Once the police have put down the riots, the rest of us have more to do than clean up the broken glass.

The writer is a former adviser to David Cameron and runs a crime prevention charity, Only Connect

Copyright The Financial Times Limited 2018. All rights reserved.