Lots of people seem to have been touched by the story of 31-year-old Sukhwinder Singh, who was stabbed to death in East London after confronting two youths who had just mugged a young woman. The Daily Express described him as “the bravest and most selfless man”, The Mail on Sunday labelled him “a hero”, while others have used his story to illustrate general points about society.

A senior police officer cited him as an example of how police should not just “allow” but “encourage” people to intervene when they see a crime taking place; the Sikh clergy embraced him as an example of the selflessness that is a central tenet of the faith and announced that his portrait would be put up in a religious museum; and David Cameron used his story to illustrate a point about broken Britain.

But the other day the Evening Standard published an investigation into Singh’s life, which emphasised a single but very important detail. It turns out that the reason Singh had not visited his family in India for a decade — not when his son Gurinder was born in 2000, nor even when his three-year-old daughter Gurpreet died in 2002 — was that he was one of Britain’s estimated 750,000 illegal immigrants. If he had left these shores, he would have never been allowed to return.

I’d like to think that this would not have changed the generous and emotional response to his story. But I suspect it would have, given The Mail on Sunday and the Express position on immigration (sample headline: “Any amnesty for illegal migrants is simply surrender”), and given that illegal immigrants are among the groups that the Conservative Party blames for breaking Britain (“Only when we have a border police force will we be able to start making Britain safer,” says the party in an online statement).

This revelation, though, if anything, makes Singh’s story even more pertinent and poignant because it illustrates a very important policy point. Namely, that Boris Johnson, the London Mayor, is right in arguing that the best way of dealing with illegal immigration is to give long-term illegal migrants — those who’ve been here for five years, don’t have a criminal record and can economically support themselves — an amnesty.

I realise that in saying this, given my skin colour, I’m inviting a torrent of horrible letters and e-mails telling me in capital letters and in violent terms to get back to where I came from, which happens whenever I mention race. Given the intensity with which illegal immigrants are despised, I think I’m going to take their advice when this piece is published and take refuge for a while in my home town of Wolverhampton.

Nevertheless, it seems to me that Singh’s case demonstrates four things about Britain’s most contentious problem:

1. Illegal immigrants are with us to stay. Of course, in an ideal world, the only immigration would be of the legitimate variety, but these people are with us and, as the National Audit Office has pointed out, deporting them would be very expensive (it would cost up to £4.7 billion). Johnson says that at the present rate of arrest and repatriation it would take the authorities more than 60 years to remove all the illegal immigrants (and lots more would arrive in the meantime); and as Simon Jenkins has argued, getting rid of them would be like trying to drain the English Channel with a spoon. “The market in migrants is like the market in guns and drugs. Governments pretend they can control it. They talk big and wave a big stick, but in truth they are impotent.” It says everything about the impossibility and futility of trying to remove illegal immigrants that no one seems to have even spotted Singh’s immigration status until several weeks after he was murdered.

2. Illegal immigration is a London problem. There are lots of weird things about the “debate” on illegal immigration: that as a nation we loathe them, but at the same time rely on them to do our worst jobs, cleaning our toilets, driving our cabs and building our office blocks; the common fear that Britain suffers more than most, when the number is actually small (the US is home to an estimated 12 million undocumented workers, more than three times as many as Britain has per head). But the paradox I find most peculiar is that the farther you get out of London, the more intense the fear and outrage. Yet people such as Singh are much more likely to end up in the capital. According to one estimate, three quarters of all illegal immigrants live in the capital and roughly one Londoner in 15 is here illegally. And they’re generally tolerated, not least because London has such a long and rich history of welcoming immigrants.

3. Long-term illegal immigrants, if embraced, would make a positive economic contribution. Those who have entered Britain by illicit means are often portrayed as parasites, a viewpoint epitomised by the pressure group Migration Watch’s claim that an amnesty for illegal immigrants would cost taxpayers £130 billion over 35 years, or nearly £5,600 for every household. But, in contrast, a London School of Economics report commissioned by Johnson found that an amnesty would add £3 billion a year to our GDP and generate annual tax revenues of almost £850 million, an argument supported by common sense — why would people come all this way and then not work? — and by Singh’s example. His boss evidently regarded him as the best concrete finisher in the firm. He was “always the first to arrive and the last to leave”, and he earned £2,000 a month, half of which he sent home. As it happens, his employers have said that he provided a National Insurance number and a tax reference number, which meant that tax was deducted at source. Most illegal immigrants don’t pay tax, which seems a daft thing to allow given this country’s precarious finances. An amnesty would lead to an immediate and significant increase in tax revenues.

4. Long-term illegal immigrants, if embraced, could be good British citizens. Those against an amnesty would have us believe that it would lead to the moral collapse of our society, but as several newspapers have pointed out, Singh worked hard to provide for his family, when he was not on the job he dedicated his time to community work at his local temple, and when he saw a British citizen in distress he went to help. He paid the ultimate sacrifice and in doing so he proved that, given the chance, he could have made a great Briton. And so could lots of others like him.

Sathnam@thetimes.co.uk

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