Of all the televisual arts, that of scheduling is the most arcane. When I worked at the BBC there was a slight, bespectacled young man called David Berg, whose brilliance was obvious, but whose true worth was - like that of his Arctic cousins - four-fifths hidden below the surface. With his charts and maps of audiences, shares and programmes, Berg plotted unbeatable combinations of shows and airtimes, matching the available viewers to the programmes. Men and women like Berg are to the Jacksons and Thompsons what Peter Mandelson is to Tony Blair. In the darkness they plot their plots, while others take the limelight. They always, always do things for a reason.

So when you have a massively expensive (though difficult) drama, and the obvious place for it is Sunday night on BBC2 (because that is when there is the optimum audience available to watch) and you decide to run it at 9.30 on Saturday on BBC2, something is going on. Either you have suddenly discovered that there are a hidden five million or so classic- drama lovers, ready and willing to forego theatre trips and pubbing for the sake of the TV - or you fear that the show's a dog.

Or (perhaps) it's a bit of both. For Nostromo is certainly semi-canine. But in a very interesting way. It is as though two entirely different films - one by Sergio Leone and one by Hugh Hudson - had been edited together, the characters from one allowed to commune with the cast from the other.

First there is The Mission II, a tale of an Englishman's burning obsession in the heat of the tropics, starring understated Colin Firth as Jeremy Irons and Serena Scott Thomas as Robert De Niro. Terrific actors ride through fantastic scenery, act against spectacular and flawless settings (though the mine itself looks like a damp valley in Shropshire I once camped in), real trains and steamboats cut their way through mountain and jungle, and there is a gripping mixture of adventure and human corruption. True, there are occasional scripting infelicities, such as the introduction of Don Martin: "Well, well. How is life in this benighted country from which my family sensibly ran away?" (To which the only answer can be, "Oh fine, fine".) But it's great.

And then, side-by-side, there is For a Fistful of Silver, in which macho Latins ride horses, get dusty and sweaty, grunt in manly monotones and throw women across their saddle-bows. Prominent among these is Claudio Amendola as Nostromo himself, his shirt undone to the waist, his favourite line being a Leone-esque rumble that "teeves deserve to die". His sidekick Ramirez is a Galliano fantasy with long hair, smouldering eyes, and no shirt at all. Together they resemble a Maltese boy-band. At one stage a character from The Mission II says of the wooden Nostromo that he "has panache". Panache must have been the name of yet another lusty mulatto lass that Nostromo had just flung over his saddle-bow.

Nostromo's foster mum is played by Claudia Cardinale - fair enough - but whenever his foster dad speaks, one hears the gravelly tones of the bloke that does all the voice-overs for the villainous Mexican baddies in spaghetti westerns.

The problem, of course, is that this is a co-production - and it is little surprise that the film has done much better in Italy than Britain. But after the experience of Rhodes, it is truly terrible luck for the BBC to be associated with two mining disasters in three months. Perhaps we need a public inquiry.

There was another curious scheduling decision in placing Breaking the Code latish in the evening on BBC1. This tale of the Enigma genius, Alan Turing, would have sat very well at 9pm on BBC2. As it was it didn't finish till midnight, which was curious. But my suspicion is that this time the production was being paid a compliment. Having been commissioned by the deeply unfashionable adult-education department, it may originally have been slated for some graveyard, Nostromo-ish slot - only to be seen for what it was, a brilliant and accessible television play.

Several reviewers have understood the play mainly in the context of the hero's persecuted homosexuality, which may have led to his suicide in his early forties. But in fact there was something else going on here.

After several marvellous scenes in which Turing (Derek Jacobi) explains his almost sensual love for science (a book is described as "audacious" and "naughty"), there comes the key confrontation when Turing confesses his homosexuality to his mother (Prunella Scales). Baffled, she says that she had always assumed that "his sort" were awkward with girls. "What do you mean, my sort?" he asks, sharply. Mathematicians and scientists, she replies. It is not just homosexuality which is regarded as being in some way aberrant, but scientific genius as well.

What Whitemore was pointing out is the lack of value accorded to our scientists, our engineers and our mathematicians, compared with that lavished upon the heroic contributions of soldiers, or the flashy achievements of artists. Men and women like Turing - who really did influence the outcome of the war - have been largely ignored. The last shot of the soulless piece of inner trunk road in Manchester that bears his name - the one commemoration of this unsung genius - told the real story.

Perhaps our attitude to things scientific is gradually improving. Certainly television has done wonders to bring the natural world into our living rooms. Following hard on the heels of Spirit of the Jaguar has been the series dealing with extraordinary migrations. This week saw Incredible Journeys: The Rattlesnake's Tale (BBC1, Thursday), in which our hero, though beautiful and a nice mover, was poor on dialogue. Since he was not (as is so often the case in BBC Wildlife docs) given a name, let us call him Nostromo the Rattler.

Nostromo was followed (at snake level) across a stretch of desert as he searched for food and sex. He failed with the latter and succeeded (utterly revoltingly) with the former. In the meantime his brothers and sisters were run over, strangled, poisoned by giant centipedes, and shot at. It was great.

But consider, for a moment, the logistics of getting all these snakes to be attacked on camera. The crew must have carried a huge basket of rattlers on location, the burden becoming lighter as the animals were gradually disposed of. They deserve medals.

Another dangerous journey was featured in Horizon: The Ice Mummies (BBC2, Thursday) - that of a middle-aged man who set out from an Alpine settlement with his herd of goats, and never returned - 5,300 years ago.

Now, I love my mummies. Their yellow, crackly skin and preserved teeth exert the same kind of ghoulish attraction as do all those weird cadavers you can see on The X Files. What is special about Otzi (as the locals have christened him) is that he has come to us complete with clothes, hair, a copper axe and a quiver full of arrows - all perfectly preserved.

Horizon unfussily told the tale of the discovery and what has been learnt as a result. But in addition to the usual cast of archaeologists and archaeo- botanists from various groves of applied academe, we were assisted by members of that odd branch of the European Green Movement - the guys who like to dress Stone Age. Men such as Hanspeter Schrattenthaler, who sat in a clearing chipping flints and told us that "personally I preferred ze copper axe to ze flint one". Thank you, Hanspeter, and now we shall some ibex chop up.

It could have been worse for Otzi. He could have answered an advert, placed by Janet Culver, an American woman, for a companion to go sailing with. The result, of course, was Disaster (BBC2, Thursday), a reconstruction of their short, but appal-ling journey.

A few miles out from Bermuda, Janet asks companion Nick: "What am I going to do if you vanish over the side?" Bad question, for - sure enough (20 programme minutes later) - Abbott goes doggy paddling 400 miles off Long Island. But not before Janet has demonstrated that the gift for understatement is also granted to our transatlantic cousins. "This trip," she says ruefully, as she settles back against the side of the dinghy, her chapped lips moving painfully and death seemingly approaching, "is turning out rather differently to how I imagined." Then: "Nick began to feel discouraged after we ran out of water." I bet that's not how they're talking about Nostromo up at the Beeb.