The Weekend's Viewing: Black Mirror, Sun, Channel 4 Japan Tsunami: Caught on Camera, Sun, Channel 4

I can't remember whether I said something cynical when Channel 4 promised that it would divert the river of money it poured into Big Brother to irrigate original, one-off dramas, but if I did, may I offer a cautious apology.

There are, as the politicians like to say, unmistakeable green shoots of recovery in the channel's drama output. Ronan Bennett's Top Boy was exactly the kind of thing a public-service channel should be doing and now Charlie Brooker's series Black Mirror is also delivering drama with thistly readiness to be difficult to swallow. Last week's "The National Anthem" put the pig among the pigeons in characteristically Brookerian style, while this week's episode, "15 Million Merits", offered a hi-tech dystopia in which the Big Brother figure was a Simon Cowell-like talent show judge. And while the first episode set out to goad and jab with the audacity of its bad taste this was far more melancholy and pensive in its tone.

Brooker's setting was a vision of consumer technology turned into a prison, with worker drones occupying cells in which every wall was a giant television screen. They wake to jaunty, nursery-school animations of a cockerel and have to pay, with "merits", for the right not to watch the programmes. Cover your eyes to take a break from the torrent of game shows, porn and X-Factor-style talent formats and the cell rebukes you, playing increasingly tormenting noises until you become an obedient viewer again. Merits are earned in what looks like a hi-tech gym, where citizens pedal endlessly on exercise bikes, racking up the credits they need to purchase everything, from a squeeze of toothpaste to an entry ticket for Hot Shot, the reality show that offers one of the few ways out.

Brooker's Winston Smith was Bing, played with numb despair by Daniel Kaluuya, and his Julia was Abi, overheard by Bing one day singing in the communal lavatory. Bing persuaded Abi to enter Hot Shot, gifting her the necessary credits. "I just want something real to happen, just once," he said, pleadingly, but once on the show she was steered, with the help of drugs and the tyranny of audience voting, into becoming a porn star rather than a singer. In the cruellest irony, Bing couldn't afford to block out the sight of the woman he loved making her debut on the erotica channel.

Determined to get revenge, Bing earned enough credits to enter himself, sabotaging the live broadcast with a diatribe about false consumerism and mob stupidity. He briefly turned into Charlie Brooker, in other words, and part of the undertow of sadness in "15 Million Credits" came from the biographical echoes in its story, with a disgusted and despairing man finding that even his rage can be repackaged for sale by the medium he deplores. The last shot showed him staring sadly out over a higher-quality virtual landscape.

It was beautifully realised, with numerous tart little touches in the design, and nicely performed too, with Julia Davis and Rupert Everett capturing the ersatz sincerity of talent show judges and Jessica Brown Findlay perfectly judged as Abi, singing "Anyone Who Knows What Love Is" with a sweetly untutored grace. When the same song returned, sung by Irma Thomas over Bing's solitary figure, I found myself thinking of Dennis Potter, who also loathed how low popular culture can sink but took comfort from its occasional heights. Perhaps the comparison's a little premature, but the fact his name came to mind at all is telling in itself.

I thought I'd seen every Japanese tsunami video shown, but Japan Tsunami: Caught on Camera proved me wrong, with footage that included a terrifying sequence shot from inside one of the cars swept away in the water. I imagine Charlie Brooker might have hard things to say about our armchair consumption of other people's apocalypse, but I couldn't stop watching even so.