Last Night's Television: Terry Pratchett: Living With Alzheimer's, BBC2<br />Minder, FIVE

Terry Pratchett – now, to his obvious irritation, the nation's most famous Alzheimer's sufferer – doesn't seem to have any trouble remembering his jokes about this fact. "My name is Terry Pratchett," he said, introducing himself to the camera, and then, after a comic beat, "at least I think it is." Later on, towards the end of Terry Pratchett: Living with Alzheimer's, the devoted fans at the annual Discworld convention got a longer variation of this gag. He's got another line he's fond of, too: a crafted turn about how his ambition is to make Alzheimer's regret it ever came down with Terry Pratchett, which tends to be deployed when he's on the chat-show circuit. And this isn't a complaint, just a recognition that being famous (for anything) is a performance, with a script, and that Pratchett shows few signs yet of being incapable of playing himself, an established connoisseur of mischievous inversions and black comedy.

The irritation, incidentally, is reserved for the fact that he now finds himself in a pigeon-hole even more constricting than that of "humorous fantasy writer". For the disease itself, though, he feels something much grander than mere annoyance, a rage that the future he'd planned for himself has been hijacked by an unpredictable degeneration. Mostly this fury is contained in those spare little jokes, but just occasionally it spills over so you can see it, as when he briefly shooed the camera away while attempting to tie his own tie. He was only doing it to show that he couldn't, if you see what I mean, but the frustration and sense of exposure temporarily became too much for him.

Pratchett has a particular form of the disease, posterior cortical atrophy, which means that his fluency and verbal invention remain largely intact, while his visual comprehension is getting more tattered. When he was talking, the disease was effectively invisible, or inaudible. But when he attempted a simple visual task, such as copying a rudimentary diagram, it suddenly loomed into view. Attempting to read a chapter of his new book to Discworld fans, he stumbled repeatedly, blaming the mishap, in a writerly combination of immediate practical explanation and ominous metaphor, on the "shadows" falling across the stage.

Having sold nearly 60 million novels, Pratchett is in a slightly better position than most when it comes to trying to keep shadows at bay. He's given a million pounds for medical research, for one thing. But he can also afford to explore less mainstream cures. "The Alzheimer's," he confessed, had "radicalised" him. "I started having heretical thoughts like, 'Why is it that medication is only available from doctors and pharmacists?'" So as well as giving personal testimony to the impact of the disease, he is also exploring all possible treatments, orthodox and otherwise. Among other bits of self-confessed straw-clutching, he's commissioned his own version of Professor Branestawm's device that bathes the brain cells in infra-red light. "So far, there's been nothing negative, which is positive," said its inventor blithely, after Pratchett had tried his treatment out for a couple of weeks. Pratchett himself stated it far more accurately: "In the world I live in, 'not worse' is almost the same as 'better'." The "almost" was crucial, and one can only hope he finds something soon that will allow him to drop it.

I fear that Minder, Five's impertinent resuscitation of one of the dear departed of popular British television, might well cause distress to anyone of failing mental powers. "Am I losing it?" they will think. That signature tune seems awfully familiar, not to mention the odd-couple relationship between the older wheeler-dealer and the exasperated young heavy. But surely it was Arthur Daley, not Archie? And what the hell happened to George Cole and Dennis Waterman? Those with fully functioning memories will recognise at once that Dr Frankenstein has been at his tricks again, plundering graves and trying to shock the resulting meat collage into a shambling semblance of vitality.

Personally, I don't feel any huge reverence for the original, so I'm happy to say that if you want cheeky-chappie malapropisms, then Shane Richie is perfectly capable of delivering them, and Lex Shrapnel, as the minder himself, is a good deal less cartoonish than his name suggests, even if he does have a comedy walk (a bit like Robert Webb from Peep Show, angling for laugh). But the script is risible in quite the wrong way, marred by a Beano crudity. It's the sort of thing in which secret plans are always in the top drawer of the desk and the villain ends up being drenched with a magically convenient fire hose so that the policewoman can say, "Only thing to do with a dirty politician," and everyone can chortle for the cutaway. "It was well worth us going through all that pavlova," concluded Archie. No it wasn't.