Media playback is unsupported on your device Media caption Youths helped the injured man to his feet, and then stole his belongings

The video of a 20-year-old Malaysian student being robbed by people who had pretended to help him has for many been one of the most poignant moments of the riots, with Prime Minister David Cameron saying it showed things are wrong in society. Why was this video of the bad Samaritans so powerful, asks Giles Fraser, canon chancellor of St Paul's Cathedral.

"And who is my neighbour?" a lawyer asks Jesus. His reply may be the best known and most morally influential of all Bible stories.

"A certain man was going down from Jerusalem to Jericho, and he fell among robbers, who both stripped him and beat him, and departed, leaving him half dead" - so begins the parable of the Good Samaritan.

A priest and a Levite hurry by, ignoring the dying man, too afraid that they are going to get mugged themselves. But a Samaritan, a stranger from a widely hated community, lifted the man off the floor, took him to an inn and paid for his care.

Being a good Samaritan has become the paradigmatic expression of good neighbourliness. Morality begins with compassion.

Metaphor for kindness Used in English to mean a kind stranger helping since at least the 17th Century

Parable only figured in the Gospel of Luke

Jesus gives the parable in response to a lawyer's question about neigbours

Jews and Samaritans were mutually hostile at the time Riot mugging victim 'recovering'

The story of Asyraf Haziq looks a little like this, at least at first.

On Monday night, the 20-year-old Malaysian student, who had only recently arrived in the country, found himself caught up in the riots in the Barking area of East End of London. On his way to buy food to break his Ramadan fast, he was attacked at knifepoint and his jaw broken.

As he sat on the pavement in a pool of blood, a group of youths gather to help him. Here, apparently, are the good Samaritans.

They appear to offer him sympathy. One offers him assistance to stand up. And then, as he staggers to his feet, a number of them open up his rucksack and rob him.

On the mean streets of London, even the good Samaritans are bandits.

The video of this robbery has now been watched on the internet well over a million times. It has come to encapsulate the moral vacuum that is at the heart of these disturbances.

Role models

"When we see the disgusting sight of an injured young man with people pretending to help him while they are robbing him, it is clear there are things that are badly wrong in our society," said Prime Minister David Cameron on Wednesday morning.

So what is "badly wrong"? Unlike the riots of 1981, these are not fundamentally about race or police heavy handedness. It is not some political grievance that rioters have in common, but rather the desire for a new pair of designer trainers and flat-screen TV.

In many places, this rioting is simply shopping without money. Yes, there will be much talk in the coming days about education and family breakdown. Feral kids, some pre-teenage, need stronger role models at home, especially from fathers. And in the absence of parental guidance, young kids look to gangs as their real family.

The Parable of the Good Samaritan A certain man went down from Jerusalem to Jericho, and fell among thieves, which stripped him of his raiment, and wounded him, and departed, leaving him half dead. And by chance there came down a certain priest that way, and when he saw him, he passed by on the other side. And likewise a Levite, when he was at the place, came and looked on him, and passed by on the other side. But a certain Samaritan, as he journeyed, came where he was, and when he saw him, he had compassion on him, and went to him, and bound up his wounds, pouring in oil and wine, and set him on his own beast, and brought him to an inn, and took care of him. And on the morrow when he departed, he took out two pence, and gave them to the host, and said unto him, Take care of him; and whatsoever thou spendest more, when I come again, I will repay thee.

But underlying so many of these problems is a general culture of acquisitiveness that has come to shape our society. "Get rich or die tryin'" advises the rapper 50 Cent. Rap music isn't the cause, it's just another symptom.

We over define ourselves by what we buy. I have therefore I am. Many of those rioting have been brought up on this debased philosophy, and have become increasingly angry at the feeling that they have been locked out of the world of material possession.

Back in 1980, then-Prime Minister Margaret Thatcher gave an important interview with Brian Walden for London Weekend Television.

It was the first major TV interview since becoming Prime Minister. She was keen to set out her stall. She would work to return Britain to prosperity. This would require deep cuts in public spending.

Walden pressed her: "Now I put it to you, is the price of our economic recovery and prosperity greater inequality in this country?"

Her answer was remarkable: "…yes indeed, if opportunity and talent is unequally distributed, then allowing people to exercise that talent and opportunity means more inequality, because there are the resources to do so. No-one would remember the good Samaritan if he'd only had good intentions - he had money as well."

Mrs Thatcher's then economic policy adviser, Brian Griffiths, told me recently how proud she had been of that answer. A year after this interview, the inner cities erupted in violence - riots widely blamed on racial tension, poverty and social exclusion.

These latest riots are bound to generate a great deal of moral soul searching. The church's response to the 1981 riots was the Faith in the City report.

Condemned by Mrs Thatcher as left-wing propaganda, it nonetheless revitalised the Church of England's engagement with some of the most deprived communities in the country.

And in the debates that are already taking place about the causes of the present chaos, no doubt one issue will be the extent to which it is a by-product of economic circumstance, of how falls in the stock market impact the poorest and the vulnerable.

Others will fiercely contest this link, arguing poverty is too often used as a weak excuse - morality first of all means personal morality, personal responsibility. Expect this argument to run and run.