Who Do You Think You Are? BBC1<br/>Ugly Betty, Channel 4

Kim Cattrall went on the trail of her runaway grandfather and discovered more than she bargained for

Kim Cattrall, who played the nymphomaniacal Samantha in Sex and the City, was the guest on last week's Who Do You Think You Are?. She brilliantly narrowed the focus of the programme. Rather than give the BBC carte blanche to nose around in her family tree and risk finding (as with Michael Parkinson) nothing of interest, she used the show like a Hollywood star employing a private dick. She wanted to find out what happened to her grandfather George Baugh, who walked out on his wife and three children in 1938. "I'm very angry at him," grated Cattrall, "and I don't know who he is."

George, it became apparent, was a hard man to know. The only photograph that Kim's mother and sisters possessed was a wedding scene from 1934: George could be seen indoors, peeping behind a curtain through a window, as the wedding party was snapped on the lawn. Kim's mum wept as she remembered her father asking her to go with him, and packing pencils and books "because he knew I liked to write". In the end she stayed, and the family endured a Toxteth childhood whose howling poverty made Frank McCourt's Limerick sound like Sandringham.

As La Cattrall visited the family records office in London and whizzed to a family meeting in Derbyshire with George's sister-in-law, it was hard not to be gripped. We learned that his own father drank heavily and that George ran away from home, to sleep under parked lorries and be brought home by the police. We found that he'd stowed away on a cargo liner to New York in 1935, but was rumbled – and returned to impregnate his wife again.

The only problem with the programme was its resplendent fakery. Every phone call, every encounter between Kim Cattrall and the next link in the chain of investigation was filmed as though au naturel but was as stylised as kabuki theatre. At one point, when the object of her enquiries wasn't home, Kim called next door. The neighbour, her hair suspiciously well coiffed, seemed unsurprised that a star of Sex and the City was on her doorstep and launched without preamble into her two-penn'orth of evidence. When they discovered that George had married again, and spawned children, Kim was given a Manchester births register to inspect; like a child with a lucky dip, she pulled more and more of George's children's names out with squeaks of glee. It was sweet, but a tiny bit contrived.

We never got to understand George (he scissored himself out of his own wedding photograph) but by the end we knew that he'd raised a second family in Australia. Kim Cattrall's attitude to him seemed equally hard to know. Despite her early censoriousness, she seemed impressed by his single-mindedness. "Wow," she said, reading his second marriage certificate, "He's a bigamist. Son of a bitch..." Later, she mused, "It's kinda despicable, he had no sense of responsibility whatsoever," and then, a minute later, "He was a very ballsy character, my grandfather – he took a lot of chances."

Her mother showed less confusion. Shown a photograph of her father, she said, "I feel nothing. I feel no connection with him at all. He had no heart. He had a swinging brick instead." It was a touchingly real moment at the end of an artificial but absorbing quest.

In Ugly Betty, our heroine was charged with taking the artwork of Mode magazine to the printers. The cover featured a spoof tornado, whipping the clothes off a model. Then a real tornado hit Florida, and Betty had to decide whether to pull the issue or let it run... The ramifications of this Homeric crisis were amusingly and cynically explored by the usual venal bosses ("Taking the fall is what the little people are for") and scumbag fashion hacks ("There hasn't been a T-shirt-worthy scandal since Winona went shopping"). By the end, though, the writers lost their nerve and everything turned cute. Her boss admitted his crime. A nice local counsellor popped round to advise Betty's sister about her business. "I'm so proud of you both," said their father, "You fought for yourselves and won."

For God's sake. Remember how Seinfeld used to insist of his writers, "No hugs and no learning"? Can we get back to the bittersweet cynicism please?