Our Home Secretary, David Blunkett, has certainly lost the plot. Faced with a BBC documentary which revealed that the Police Training Centre at Bruche, near Warrington, Cheshire, harboured the vilest forms of racial prejudice and hostility to blacks and Asians, he turned his guns on the programme-makers. He wasn't questioning the BBC's right to expose racism, but their "intent to create, not report a story". This is so much tosh.

Mark Daly, a BBC reporter, signed up as a recruit at the centre in order to investigate the progress made by the Greater Manchester Police in eradicating racism, after its chief constable had admitted in effect that his force was institutionally racist. Imagine that Daly and the BBC had announced their intention to film at the centre for this purpose. Even if they had been given permission, everyone would have been minding their p's and q's to ensure that all was hunky-dory. The press office would have taken charge and a minder would have been assigned to accompany the crew just about everywhere it went. I have seen many of these programmes made from the inside. I made one myself, which revealed hardly anything about race and only the absentee culture at Brixton police station.

The result of the filming was not a news story as we usually see it on the BBC news, but an investigative documentary of the sort that has been at the heart of British broadcasting and written journalism for as long as I can remember. Daly was not reporting a story that was already out in the open, but finding a truth that existed under wraps. Only undercover reporting would drag it out. For this, we ought to commend the BBC.

Within the past month, 12 policemen have either resigned or been suspended on matters to do with race - eight as a result of the BBC investigation, four after a campaign by the family of Roger Sylvester, who died in 1999 a week after Scotland Yard officers visited his home in north London. If we depended on internal checks and balances, these people would still be working.

There is more to come. On 17 November, several black police officers and their supporters will demonstrate in the streets against racism in the force, after years of battle in which they have made no progress whatsoever. The police service is now virtually the only public body where racism is still a major problem. But there will be no change while Blunkett is at the helm.