What these home-made reports restore is what professional polish inevitably removes - a sense of unforced incredulity at the ways of the world
"It wasn't at all what I'd planned for my retirement," said Margaret Gibbins, a bank manager's wife from Cornwall. I don't know what she had in mind - watercolours or hang-gliding - but what she'd ended up with was a part-time life as an investigative reporter. For three years now, Mrs Gibbins has been taking a video camera into livestock markets, focusing on the sizeable gap between what the law (and the industry itself) say they should do and what actually happens.

In Private Investigations - a new series which exploits the growth of camcorder activism - you saw the results of this unconventional pastime. Not all of her clips were equally convincing. Footage of a cow being tapped with a stick didn't seem to offer evidence of systematic brutality and other contrasts between the letter of law and the reality suggested that it was the words that had lost their way rather than the deeds. Is the injunction that cattle should not be driven over slippery ground really compatible with any sort of farming at all? But other scenes made it clear that tender sensibilities are not exactly nurtured by the trade - a drinking trough overflowing with faeces, a farmer kicking a reluctant sheep, a man tugging a frightened pony by the tail.

What Mrs Gibbins brought to these unwholesome sights (which, after all, have featured in other documentaries before) was a useful quality of naive indignation. At one point, after talking to an expert who insisted that animals could suffer, she said: "I was hoping for an equally enlightened attitude from those that run the markets". A more cynical reporter would have been hoping for the exact opposite - a florid-faced bully who would give the adversarial encounter a certain gross clarity. In other words, a reporter would be looking for good television, whereas Mrs Gibbins is looking for better animal welfare - and the clumsiness of her presentation (the stiffness with which she reads the links and the little moans with which she betrays her distress) reassure us of the purity of her intentions. These home-made reports don't really offer a different agenda to that constructed by conventional television or even different images (most people know the conventions well enough to ape them). What they restore is what professional polish inevitably removes - a sense of unforced incredulity at the ways of the world. I find myself quite unable to decide whether this is a good thing or not, but it certainly seems to meet the mood of the times - with its distaste for formal protocol and it's unquestioning appetite for emotional sincerity.

The evening also offered two engaging exercises in contemporary history - Marc Bolan: Dandy in the Underworld and Black Wednesday, a cool account of the torrid day on which the government's economic policy fell to bits in its hands. Best detail from the latter was Kenneth Clarke's recollection of the moment when three senior cabinet ministers found themselves hunting around for a transistor radio in order to discover how many more billions of public funds had gone down the drain. But there was also a striking cameo appearance from Kelvin MacKenzie. He recounted, complete with impish impersonation, how the Prime Minister had telephoned him to find out where The Sun stood. He replied with the dignity appropriate to his position: "I have on my desk, Prime Minister, a great big bucket of shit and I intend to pour it all over you tomorrow." "Oh, you are a wag," replied Major, with all the dignity appropriate to his.

Dandy in the Underworld steered a diplomatic course between dazed disciples ("Marc had a knowledge that goes beyond learning") and the openly scornful - in his later career, when arrogance and drugs had destroyed his elfin appeal, one journalist gave him the memorable title of "the glittering chipolata". I learnt quite a lot about Bolan: that he was originally championed by John Peel until he abandoned his folk roots for stardom, that his charm was in inverse proportion to his success, that he championed the cause of much younger musicians. I'm not sure that I wanted to know any of it but the process of education was surprisingly painless.