Last Night's Viewing: Granny's Moving In: a Wonderland Film, BBC2<br />Venice 24/7, BBC4

Like autism, Alzheimer's disease has a dangerous tendency to go pastel on screen. By which I mean that television treatments of these conditions are inclined to turn up the brightness. The darks are less dark and the lights are foregrounded. It's not a pernicious instinct, really, more an instinct of solidarity with those who have to live with the consequences. It has one hazard, though, which is that it can sentimentalise painful and difficult circumstances. The audience (those at least who have no more direct knowledge) visit as tourists, alert to the picaresque and colourful aspects of the scene before them but less aware of the hardships they entail. And at first, Granny's Moving In, Paddy Wivell's film for the Wonderland strand, looked as if it might be guilty of that sin of omission.

Granny was to blame, to be fair. As her exasperated daughter Sue said: "Peggy's a one-off... she's not your normal sit-in-a-chair-and-knit-type lady." At the beginning of the film, Peggy hadn't received a diagnosis of Alzheimer's but had vascular dementia, a fact that didn't seem to have cramped her style at all. A cheerful bustling type with a white bob, she chattered away brightly to anyone who would listen. She also loved to head off into London on her free bus-pass, accosting tourists with grandmotherly advice. "Are you sure you're warm enough?" she asked a startled man in shorts in Trafalgar Square, before tottering off to plonk down next to another couple and nag them genially about their smoking.

"Basically she's 10... she relies on me to look after her really. She sees through the eyes of a child," said her daughter, who (along with Peggy's son-in-law) had decided to sell their separate houses and build her a self-contained annexe in the garage of a new bungalow. Before the work could be completed, though, they had to live together in Sue's house, and that's when Wivell let you see the harsher friction. For a 10-year-old child Peggy had quite a mouth on her, not to mention an unnervingly blithe attitude to her own incontinence. "I think you left a damp patch on that bed," said Sue, hurrying her out of the shop in which they'd been shopping for Peggy's new furniture.

At turns, Peggy was charming and infuriating, cracking jokes about her passion for dancing at one moment, stubbornly sabotaging her daughter's attempts to pack up for her at another. But neither she nor her condition were, in the end, sentimentalised. "Why are you talking to me as if I'm a fucking imbecile?" she screeched at one point, frustrated by the strange switch in which she'd become the rebellious teenager and her own child was now a rebuking authority. And Wivell ended with nicely weighed ambiguity too: "I couldn't wish for a nicer daughter," said Peggy, happily ensconced in her deluxe garden shed living room. But then you had a matched image of her looking out alone through the window and Sue and her husband behind their sliding doors, a family separated by what Larkin once called "sun-comprehending glass".

Venice 24/7 was pretty much as boring as every flashing blue-light documentary, the addition of millions of gallons of tidal water and some very fine quattrocento facades not really doing a lot to revive this horribly overworked genre. I guess it's quite interesting that Venice now has a female fire chief (battling against what look to be a gracelessly misogynistic set of colleagues) and reassuring to find that even native Venetians get lost in that maze of alleys and fondamenta. But not quite interesting enough, I would have thought, to justify a six-part series, given that most of the "shouts" are almost identical. The bottom line is this: the fire-engine's a boat, and the ambulance and the hearse. Otherwise, they do exactly what they do here.