Back in the days when railways were shockingly newfangled, tea could provoke a minor crisis, or so you'd have believed if you'd watched the finale of Cranford (BBC1). This radical, but successful, amalgam of three Elizabeth Gaskell works about a gossipy, quaint Cheshire town in the 1840s bowed out in true Sunday night costume drama fashion: genteel tragedy leavened with community spirit and improbable happy endings. To the end, the citizens continued to refer to each other as Mr/Miss/Mrs - after all, the story was penned by an author still generally known as Mrs' Gaskell.

Miss Matty (the magnificent Judi Dench) was persuaded, with difficulty, to swallow her pride and resort to trade to offset debts incurred by the collapse of her bank, opening up an implausibly successful tea emporium in which patrons who asked for the green variety were upbraided. Meanwhile, Philip 'Life on Mars' Glenister (his accent proving geographically imprecise to the last) was busy dying as the gruff, but noble, Mr Carter in near-messianic fashion: his demise, following an explosion, plucked a protégé out of poverty, led to the founding of a school and enabled haughty Lady Ludlow (Francesca Annis) to repay a mortgage. Then not one, but two, absent characters turned up from India, and unrequited couples discovered romance; it made the average Dickensian yarn seem like docudrama. Incidentally, Cranford was first published in 1851 in the magazine Household Words, which was edited by Charles Dickens.

Mrs Gaskell isn't particularly fashionable now, yet the original Cranford is a more accessible novel than some viewers may assume, after seeing this parade of bonnets and forelock-tugging. But it is substantially different - no hearthrob Dr Harrison, for a start.

Bears are in fashion. No environmental protest is complete without a polar bear outfit, and when Monday's schedules pitted the creatures against one another, the white variety trumped its inland cousin. While dear old David Attenborough was murmuring about two families of Canadian black bears mooching around the Whistler Mountain ski resort in Canada, in Bears on the Black Run (BBC2), Nigel Marven was in northern Canada with Polar Bear Week for Five. Marven - who read botany and zoology at Bristol - wasn't more educational, but he was more entertaining, and that's what counts these days. He burbled about bears, arctic foxes and owls in a chirpy twang (more TV-friendly than Attenborough's received pronunciation) - and even rolled around to make a snow angel'. Would the former controller of BBC2 be heard saying "Snowflakes are such fun when you catch them on your tongue"?

It was occasionally informative; Marven flung boiling water in the air to show the -30C chill froze the liquid before it hit the ground.

The advertisement breaks included a plug for the film The Golden Compass, featuring - you've guessed it - polar bears. And there was a mention of the Royal Institution Christmas Lectures, which Five acquired in 2005 as a fig leaf to convince advertisers it didn't just cater for the lads' mags crowd. (These days, US crime shows have taken the place of the naughty 'documentaries'.) Back on BBC2, Dr Iain Stewart concluded his globetrotting mini-series, Earth: The Power of the Planet, with a look at our place in the solar system. It didn't begin promisingly. A view of the globe was accompanied by the faintly lupine boffin intoning "This is Earth, our planet" for the benefit of morons who assumed it was Jupiter; trendy choppy editing later threatened to induce nausea among sensitive viewers.

But it settled down as Stewart set out a coherent narrative, albeit bolstered by sweeping hypotheses and faux naïveté, such as apparent astonishment that a laser beam takes only a couple of seconds to zip from Earth to the Moon and back. He finished with the solemn warning that while the planet can - given time - survive trauma, we can't. "It's not the planet we should be worried about, it's us," he cautioned. Stewart was a relaxed, enthusiastic presenter. But then wouldn't you be, if the BBC was bankrolling your tour of the most fabulous spots on the planet - while warning about climate change?