Ruby Wax with Liza Minnelli (and Husband) BBC1

Cutting Edge: Bad Behaviour C4

Confessions of a Cad C4

Watching Ruby Wax leeching on to Liza Minnelli and husband David Gest last week was like spending too much time in the company of toddlers with a heavy sherbet habit. I like Ruby Wax, but is it too much to expect that she might occasionally consider SHUDDING THE HELL UP?

Unsurprisingly, Minnelli, the alleged subject of the film, barely got a word in as Wax and Gest (and what a great showbiz law firm that would make) whooped and bellowed and groped and giggled and generally showed-off exhaustingly and tiresomely for the cameras to the point where I briefly succumbed, unprofessionally, to some 'la-la-la' with fingers in ears.

'Here's Judy Garland's little girl GETTING TONGUED!' shrieked Wax of Mr and Mrs G's wedding video. Like we couldn't SEE THAT FOR OURSELVES! At Harrods, where the threesome popped by for some spontaneous retail therapy, Ruby and Gest mugged for the bemused shoppers while, entirely out of shot, Liza waited for her fairground barkers to pipe down, perhaps wearing that startled fawn expression that is so at odds with her dirty cackle.

As Ruby's cameras stayed, inexplicably, focused on Ruby, over at the edge of the screen you could see the punters asking permission to photograph the real star. I am fond of her but here she was rarely less than slappable.

Still, if you looked hard enough you could learn just a little about her alleged interviewees, like the fact that Mr and Mrs G really do seem to be in love, albeit a 'hey kids, let's do the show right here' sort of love. And there was a minor revelation when Liza explained how she'd gifted Michael Jackson the bendy-backwards shuffle he subsequently incorporated into the moonwalk in return for some vaudeville-style tap-hop steps (non-technical descriptions writer's own, unfortunately). Heiferishly, Liza with a Zee demonstrated that she can still hoof.

The scene set in west London's finest chippy, the Seashell, where the trio turned up to serve cabbies a takeaway while Liza practised her Mockney, was excruciating and as good a cue for kettle-boiling as any. But we were soon off to Gest's fiftieth birthday bash, at which the couple partied with Lionel Blair, Bob Geldof, the Cheeky Girls, Michael Winner, Joan Collins, Diana Rigg and Tracey Emin, some of whom they might even have known.

At the end of the evening, Liza gave hubbie a little birthday cabaret which revealed, sadly, that while she may have added a Waxumentary to her CV Minnelli also appears to have lost her voice. Be warned: this week Wax meets Jim Carrey, a prospect which makes waiting to catch a BA flight look like the perfect mini-break.

C4's Cutting Edge: Bad Behaviour, focused on a less privileged problem child: seven-year-old Georgina, only offspring of Fred and Diane. The effect of generations-worth of marrow-chilling lovelessness made for a story that was, by turns, terrifyingly sad and extraordinarily moving but, finally, left you filling as though your heart had been pumped full of helium.

Fred and Diane are not, by their own admission, your 'average socially acceptable couple'. Diane is 38 but disguises her relative youthfulness with a studied and self-loathing brand of dowdiness, while Fred is 20 years her senior and several inches shorter than his wife.

Diane works for the Inland Revenue, while Fred, ex-RAF, now makes wedding videos and enjoys playing one of those old-fashioned bells-and-whistles, oompah-pah-bossa nova electronic organs you might have thought had gone the way of Ford Anglias and the Ronco Buttoneer. Their home was a stylistic relic from about 25 years BCR (or Before Changing Rooms ).

When Diane got pregnant at the age of 30, she was 'immersed in my career', while Fred already had two adult children and wasn't sure he could face doing it all again, so, into a highly hostile atmosphere, little Georgina arrived prematurely at 32 weeks. 'It wasn't our baby; it was a blob in a box,' said Diane.

Seven years on and Diane was still enraged by motherhood: 'Why does anybody have a child? It's just bloody hard work. I suppose if you've got the love there it isn't, but all it was was bloody inconvenience, expense and a curtailment of our social life. For WHAT?'

Despairing of Georgina, whose wilful bad behaviour was testing the admittedly fragile limits of their endurance, the couple had contacted social services, begging them to take their daughter into care. 'I just want it removed,' explained Diane, the mother who had never kissed her daughter goodnight. But while they waited for a decision, Fred trawled the internet searching for some sort of last chance, and - praise be - found Warwick.

We only saw Warwick once, but then so did Fred and Diane - they stayed in touch daily by phone - while Georgina never saw him at all. An ex-teacher, Warwick has a simple and highly effective system for dealing with difficult children based on rewards for good behaviour, sanctions for bad and firm-yet-loving boundaries. But, of course, it wasn't Georgina who was the problem, it was Diane and, if only because of his collusion, Fred. To their considerable credit, the couple not only accepted being told this, but worked on changing themselves even as they tried to change Georgina, a bright, pretty, desperately lonely little girl who had been misdiagnosed with learning difficulties and prescribed Ritalin for her angry hyperactivity.

Looking back through old home videos, Fred and Diane came across footage of four-year-old Georgina crying and swaying from side to side, desperately trying to attract the attention of her mother who sat rigidly, ignoring her, radiating rage.

Thanks to Warwick, the scales had been lifted and Diane could now see the horror of this almost as intensely as we could: 'If it wasn't me, I'd be reporting the mother to social services. You want to get into that film and cuddle her, don't you?' She wasn't referring to herself, but at that point Diane looked like she could use a cuddle, too.

It wasn't entirely plain-sailing but six months later, the family had been transformed into something functional. They'd fucked Georgina up, her mum and dad, but with the right kind of help, they'd been intelligent enough to change and so they deserved to end up, eventually, with the daughter they got, which is to say the one they'd probably always dreamed of having. This was a very special and powerful film.

I've never entirely bought into the notion of James Hewitt as Public Enemy Number One, given that Diana was probably the worst thing ever to happen to him and he is so obviously doomed to live with her legacy for the rest of his life. The man hasn't even committed a crime, so in the event of, say, a Hewitt v Archer celebrity boxing match I'd be rooting for James every time.

C4's Confessions of a Cad was an occasionally humourous, if very cheap, shot at a man who practically walks the streets of London SW3 with a target tattooed on his forehead. Sure, he's a caddish Tim-Nice-But-Dim-ish twit-toff of the very first order (there was a priceless scene in which he lay in the bath smoking a pipe and outing himself as a breast man: 'They do make sense, wet nurses, don't they? Who'd want to suck their mother's tits when there's a perfectly good nanny?'), not to mention a chap with the thickest skin this side of a pachyderm, but courtesy of some very suspect editing, C4 also made him out to be a morally bankrupt bastard, which is probably pushing it a bit.

However, the most interesting part of the programme didn't feature Hewitt at all: it was an interview with his ex-girlfriend, Emma Stewardson (described bounderishly by Hewitt as 'a stupid, mad woman'), whom he had two-timed for years with Diana. Now married and living in Wales, Emma looks like a perfect pedigree Diana-Camilla cross and it was impossible not to warm to the woman when she introduced us to a dog called Tess with the description: 'She's James's old dog. Another of James's old dogs.'

'Me, my family, the whole country, we all wish [Hewitt] would go away and shut up,' she said wearily while tending her Aga. When the interviewer pointed out the physical similarity between her and Diana, she sighed: 'There was when I was about three stone lighter. But she won. She won hands-down in every department. The public thought of her as an angel from heaven and I had this very different knowledge about her. I knew things that no one else knew.'

Precisely what these 'other things' were we didn't find out, which is unfortunate because, even in death, Diana is infinitely more interesting than a live James Hewitt, though possibly not quite as interesting as Emma.