In spite of accumulating countless TV documentary filmmaking ‘air miles’ over the last thirty-odd years, I found Rivers of Blood: 50 Years On a highly challenging project to work on for a variety of reasons. To begin with, aside from producing and directing this landmark 90-minute documentary for Channel 5, I chose to do most of the filming as well.

Casting was tricky, too. Not least as my vision for the film involved approaching the half-century of British race relations since Enoch Powell’s epoch-making speech from a deliberately non-white perspective. In addition, I wanted to canvass a representative cross-section of black and minority ethnic (BAME) opinion from all over the country on this perennially sensitive topic. My ambitions for the film resulted in my casting producer recruiting five families from various ethnic and religious communities, from as far field as Inverness in the Scottish Highlands and Hayes, Middlesex.

To complicate the matter further, I decided I wanted to interrogate three generations of the same clans: the pioneer immigrant cohort, who witnessed and lived through the aftermath of Powell’s invective; their (largely) British-born and -raised children; and their progeny. Though not all the interviewees made the final cut, I felt it was vital to present a smorgasbord of views about life in Britain over the last five decades, from a variety of perspectives. Ultimately, the responsibility for this fell to a Scottish Sikh family, one each from Ghana and the Caribbean island of St Kitts, and Muslim families of Pakistani and Bangladeshi origin.

It speaks volumes for the enduring resonance of Powell’s Rivers of Blood address that you can go online right now and buy a t-shirt bearing the legend: ‘Enoch was right.’ Since his incendiary speech transformed him overnight into a recruiting sergeant for an openly anti-black British nationalist sentiment in 1968, the then-MP for Wolverhampton South West has been a poster boy for white Britons who despise the concept of living amongst non-white Britons in a multicultural society. Indeed, “Enoch was right” has become an oft-repeated mantra for everyone from Tory MPs to right-wing newspaper columnists. This sentiment appears to enjoy support at grassroots level, too. Last year, a NatCen survey found one in four respondents described themselves as racially prejudiced. Tellingly, the figure has “never fallen below a quarter” since they first posed the question in 1983.

The corollary is seen in the general trajectory of the BAME experience of living in the UK. As much as most of us purport to cherish our diverse, multicultural society, the evidence of ingrained racial and religious discrimination is overwhelming. Over the decades, countless studies, reports, opinion polls and whatnot have shown people of colour experience significantly worse outcomes in education, employment, housing, health, the criminal justice system and so on, than their white peers.

Yet it is not all doom and gloom. British race relations are virtually unrecognizable from the era of unregulated racism that ended with the Race Relations Act of 1968. The idea that Powell’s old parliamentary seat is now occupied by Eleanor Smith MP, a black Brummie of Jamaican ancestry, would have been unthinkable even thirty years ago. (That said, it took till 2017 for the West Midlands to elect the region’s first African-Caribbean representative.) Again, the pace of racial change is reflected in the fact that people who identify as ‘mixed race’ constitute Britain’s biggest ethnic minority.

I confess to being profoundly shocked and not a little disappointed at the admission by most of our youngest interviewees that they had never heard of Enoch Powell. But after a short while I figured why should they? After all, I had to study race relations at university to learn about Oswald Mosley and the British Union of Fascists. The youths’ ignorance of Powell reminded me that every generation of immigrants and their British offspring suffers its own bogeymen. It was instructive that Nigel Farage’s name got called several times by the next generation.

For their parents and grandparents, Powell’s legacy has a welter of different meanings. For Irfan Ajeeb, the son of Bradford and Britain’s first non-white Lord Mayor, it is a reminder to prepare his three young children to deal with the racism he is convinced they will experience. Julian Ansah is adamant that Powell was plain wrong. He speaks to the positive contributions people of colour have made and are making to British society. “It’s just so rich,” he says, “It’s making Great Britain greater.” But probably the greatest repudiation of Powell’s racist scaremongering is the reality that, in spite of any racial prejudice or discrimination they may have encountered, the vast majority of the film’s contributors were proud to identify as an albeit qualified type of British citizen.

Rivers of Blood: 50 Years On airs 10pm tonight on Channel 5