Only a quality drama, possibly one of the best dramas this year so far, could accentuate atmosphere with the hollow chink of cheap china. The background scenery of The Curse of Steptoe (BBC Four) - the far from Swinging Sixties, gloomy rehearsal rooms, pretty policemen out to entrap in public lavatories - was evocative enough, even without the central drama of the desperate lives of Harry H. Corbett, who played Harold, and Wilfrid Brambell, who played his father Albert in the hit BBC series.

The tough, funny, sad script (Brian Fillis) and the subtly glorious performances of Jason Isaacs (Corbett) and Phil Davis (Brambell) revealed the parallel between the trapped, curtailed lives of Steptoe and son and the unfulfilled, unhappy actors who played them.

Corbett wanted to be a serious actor, the papers once called him “the English Marlon Brando”; Joan Littlewood, radical doyenne of Stratford East, was an early mentor. When he was first offered Steptoe he saw it in social-realist terms: “It's not a sitcom, it's more like Beckett.” Brambell walked in dressed as if a smart commuter, nearly an hour late to each rehearsal. Apparently they didn't like each other, but in this drama that hostility wasn't evident apart from the odd niggly outburst. Instead there was a mutual silent sympathy; they both loathed the monster they had helped to create and to which they were hopelessly yoked.

Steptoe's writers, Ray Galton (Burn Gorman) and Alan Simpson (Rory Kinnear) and their BBC overlord Tom Sloane (Roger Allam), tried to gee the men along - and their creative energy was a warm distraction from the stars' unhappiness. But the vibe in the rehearsal room was toxic, sometimes literally given the amount of booze that Brambell was necking. Every time on the show that Corbett's character snivelled about how he was trapped for ever, he could have been crying for his own career: “Finney” was doing Macbeth, while he was raking it in as a sitcom star, and Clare Higgins as “Joan” looked at him with such professional disdain you (and he) recoiled.

Davis as Brambell was astonishing - initially the older man was outacted by Corbett, who was convinced the show was about Harold. But then Brambell/Davis dredged up that ferrety gurn and wheedling voice. He was an old-school closet gay: the first time we saw him go cottaging he rapped on a cubicle door with his cane, interrupting the two men inside having sex, and shouted abuse. He went to a gay bar and a regular mocked him: “You dirteeee old man!” He would never go out with Corbett or the production team. He sat in a chair at home, ordered prostitutes and looked stricken.

Corbett's relationship was crumbling: he tried to control his then-wife, Sheila Steafel, telling her what to wear, forcing himself on her and deriding her career. Brambell was arrested for importuning. “I'm not a homosexual,” he declared. “The very thought disgusts me.”

Michael Samuels's brilliant drama followed both men's attempts to escape: Brambell resigned in shame to go to Broadway but came back after his show flopped; Corbett tried to forge a film career but the director wanted him to recycle Harold. In one interview, Corbett pretentiously waffled on about timing and being true to the subject matter. The truth was Steptoe had brought him fame and fortune but at a deeper price. “Is it f***ing worth it?” he asks Brambell.

Steptoe and Son lurched into the colour era: Brambell's sideburns grew bushier, Corbett's waistline thickened. “Cheer up, we're legal now,” the show's gay dresser tells the permanently scowling Brambell. “Actors - they're all poofs,” Albert spits with real venom on the show, sneering at Harold's preparations to be a thesp; which include, horribly ironically, Brando's “I coulda been a contender” speech from On The Waterfront - another painful echo of what might have been for Corbett.

In a wonderful, moving moment, Corbett pleads gently with Brambell: “Let's not do any more, right?” Brambell smiles a silent assent. “Goodbye father,” he says in Harold's querulous way. “F*** orf,” Brambell replies, as Albert but momentarily tender.

That would have been a nice ending, but Corbett and Brambell never escaped the sitcom's shadow. In the final scene Corbett's agent tells him there is no work bar panto and an offer of a stage tour of Steptoe and Son in Australia. The awful inevitability of what happened next flashes across Corbett's face.

Out of the Box

We know the pictures too well: prisoners hooded, balancing precariously on boxes, stacked naked on top of one another; the arrogant, laughing faces of US servicemen and women presiding over the hell of an Iraqi prison. Last night's Ghosts of Abu Ghraib (Channel 4) focused on the extreme and inhumane methods of American military interrogation at the prison; and how the soldiers who participated in it viewed their behaviour now. For me, the grist the documentary needed to move the story forward came in a question at the end: how far had the chain of command extended? That remained unanswered.

One thing to whet your appetite (though spoil none of the immense fun of the new season of The Apprentice, starting next week): wait till you see the men's hair. Big, complicated and transfixing.

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