Using a collection of news reports, eyewitness accounts, interviews, abstract images and music, they traced memories of immigration to Britain in the early 1950s up to the point where racial violence exploded more than 30 years later.

One of the many moving aspects of the film was that, although it was made by the children of these immigrants, their agenda was not simply to highlight their suffering.

They also reminded us, with enormous empathy, of the stress and bafflement that had been experienced by the largely white, working-class British community suddenly subjected to a culture change by a group of complete strangers.

It was a beautiful film, and unsurprisingly it won sackloads of awards.

It came to mind while watching Nick Griffin giggling his way through a ­relatively easy ride on BBC1’s ­Question Time.

When it came to the question concerning why so many people had voted for the BNP, there was the usual pat responses from the politicians. It was because of the MPs’ expenses scandal. It was BNP distortions made to an electorate who didn’t understand what racist, anti-Semitic, homophobic ratbags they were really voting for.

That was the issue dealt with, Griffin chuckled, twitched and writhed and they all moved on.

But one answer to that question lies within Handsworth Songs, and Griffin’s current media omnipotence might be more easily explained by the fact that this answer is rarely given proper airing.

We’re not allowed to say that multiculturalism is a mess. No-one is allowed to talk about the lives Mr And Mrs Ali, who might have wished to take a bigger part in British society if they hadn’t been called “Paki” every second day by some low life, their children denied interviews for jobs because of their family name, and found themselves isolated because local social life, around pubs and parties, was in opposition to their religious and cultural beliefs.

Nor can we talk about Mr and Mrs Johnston in the same town who find their street has filled with people who talk a language they don’t understand, whose cultural practices are either bewildering or repugnant to them, who make them feel isolated and “other” in an area in which they used to feel they belonged.

They can’t talk about it because every time both communities try to, they are shouted down by middle-class, university-educated people in Hampstead and Islington, who sit in parliament and write for The Guardian, and tell people in areas of racial and religious tension how they ought to be feeling.

The people of Handsworth, Tower Hamlets and Bradford ought to be ­celebrating “diversity” and “vibrancy”, not experiencing miserable lives full of resentment, social isolation and tribal hatred. To dislike your changing community is “racist” if you’re white and “extremist” if you’re Muslim or black.

This, surely, is one of the main reasons that Griffin and his thugs have taken votes from people who are neither inherently racist nor hate-filled, but are just unhappy and lost, living as experiments in a social Petri dish, where neither their consent nor their approval has been sought.

That’s the mess we’ve made so far. The next terrifying chapter is that we learn nothing from it. Our First Minister is very keen indeed on multiculturalism. Alex Salmond’s favourite phrase, oft repeated, as if he bought it online and has to keep using it to get full value, is that “there are many shades and strands in the ­Scottish tartan”. He backs this up by saying that “different traditions do not undermine Scottish culture – they enrich and enhance it”.

That sounds absolutely gorgeous. Who on Earth wouldn’t want that? But what does it actually mean? Which incoming traditions and which bits of Scottish culture is he referring to?

For instance, do those who arrive from a variety of countries still adhering to unreconstructed traditions including gender separation, rigid caste systems, house-bound women, and contempt for homosexuality, really enrich and enhance Scottish culture?

In what way do they? Where’s the benefit and enrichment? Perhaps Salmond has a secret plan to better integrate communities that currently don’t very much care for the way each other lives. If so, why hasn’t he shared it with his colleagues in England? Given the building pressures, one imagines they’d be very grateful.

It’s vital to ask these question now, because if we decide to move towards an independent Scotland we should, unlike the people of Handsworth, have the opportunity to have a say in how our country might look. We need to be absolutely crystal clear about its future, its shared core values and its long-term cultural intentions.

The SNP have declared themselves to be very much the party of God, so perhaps the First Minister has a theocracy in mind for an independent Scotland.

We’ve seen how our Justice Minister gives way to a “higher power” in matters of conscience, Salmond’s door is always considerably wider open to religious leaders than to any other minority special interest group, and his relentless perusal of Scots Asian voters is almost solely confined to religious ones.

The secular, non-religious, Scots Asians I grew up with, who like to be defined as “quantity surveyor” or “teacher” rather than as “Sikh”, “Hindu” or “Muslim”, are understandably not very impressed.

We need to know what Salmond’s multi-cultural Scotland will look like in reality, and how he will, unlike his Westminster colleagues, avoid self-protectionist immigrant ghettos, white elitism and diametrically opposing cultures jostling for social supremacy, and instead deliver this new “enrichment”.

We also need to know if we are going to be voting to go back to a pre-Enlightenment, hyper-religious society, where a mixed bag of faiths and superstitions are given precedence in policy-making, power-broking and cultural changes, and will over-ride secular rationalism.

Not speaking freely and frankly on these issues helped the rise of the stupid and nauseating Nick Griffin. Let’s not make the same mistake in Scotland. Start getting more specific, Mr Salmond.