Last Night's TV: A tragicomic postcard from the edge

Poppy Shakespeare, Channel 4; Marty Feldman – Six Degrees of Separation, BBC1

Mental illness has been the subject of quite a few good novels but not many films, or at least not many that I can think of offhand. Perhaps that's partly because the whole business of writing and reading a novel is not that far from a kind of mental illness: isolation, self-involvement, paying attention to the voices in your head are part of the package. Films, on the other hand, are an inherently gregarious, extrovert business: you won't do well if you can't relate easily to other people. So films tend to go for a flamboyant, entertaining, even cute version of mental illness that doesn't have a great deal to with how most people experience it.

Poppy Shakespeare at least came to the screen with a veneer of authority, being based on the much-praised novel by Clare Allan, who has spent much of her life as a psychiatric patient. The action was set in the Dorothy Fish Day Hospital in north London, a place where patients – "dribblers" – arrived dutifully to swallow their medication and spend the day being bored. For most, the main aim was not to be discharged into the community – this included the narrator, N (played by Anna Maxwell Martin), a pallid, untidy woman, forever shrinking self-effacingly into the collar of her anorak. The tedium was broken by the arrival of Poppy (Naomie Harris), glamorous in leopard-skin coat and precariously high heels, and defiantly sane. She'd been referred after some alarming answers to a job-centre questionnaire, and wanted to get discharged so that she could look after her daughter. N, smitten, became Poppy's mentor in the ways of the hospital, and tried to help her appeal against her diagnosis. But it turned out that you only qualify for "mad money" to pay for the appeal if you admit that you're ill. Soon, Poppy was blending in with the regulars, shuffling around in an old parka, pulling out her own hair, even pouring boiling water on her arms. Meanwhile, N was smartening up, putting on lipstick and wearing leopard-skin herself. Soon, she was facing the horrifying prospect of being discharged, while Poppy had been dragged ever deeper into the mental-health system's coils.

I was going to write that the casting of Maxwell Martin was inspired, but I suspect that she was the obvious choice: who else has such spikiness and vulnerability, such old eyes in a young face? And Harris was good, if not as arresting, as Poppy. They had excellent support, particularly from Jonathan Cullen and Tessa Peake-Jones as the ward doctors, full of bright, meaningless encouragement (throwing N out into the "community", Peake-Jones intoned: "You can be anything you want, N, anything. You have the power! Take life by the horns! Step into your dreams!"). Benjamin Ross directed with some flair, interspersing the gritty reality of a run-down psychiatric hospital with visionary sequences – the lights flickering insanely in a jammed lift, camera whirling round N and Poppy as they turn a therapeutic exercise into an ecstatic dance.

All the same, it felt flat. Poppy's descent and N's mirroring rise felt formulaic, and Allan's literary roots showed a little too plainly: Catch-22, Kafka, as well as, obviously, One Flew Over the Cuckoo's Nest. A lot of the problem lay simply in the transfer from page to screen, not just because of that enforced gregariousness, but because things on screen are real in a way they aren't on the page. N's narrative had fantastic elements, often with a satirical edge – there was an unspoken polemic here about the NHS's culture of targets and economies, but her subjective fantasies were shored up by the camera's air of objectivity, which gave fantasy and gritty reality exactly the same look, so that I couldn't sort out romance, satire, and documentary. A sweet, enjoyable film, but something harsher was missing.

The title of Marty Feldman – Six Degrees of Separation was a slightly clumsy way of pointing out that Feldman worked with everyone. In his early days, writing in partnership with Barry Took, he supplied gags to Frankie Howerd and was responsible for the glories of Round the Horne, a radio comedy that's to my taste survived far better than the Goons. In the Sixties, he worked with David Frost and most of the Pythons. Michael Palin and John Cleese turned up here to pay tribute to his talent, but also to remember with a little bitterness how swiftly he went all Hollywood on them. TV stardom took him to America, where he made a succession of terrible films with Mel Brooks. Among those paying homage were Gene Wilder, Barry Levinson, Larry "M*A*S*H" Gelbart and Dom DeLuise, who for some reason brought along a parakeet that did a trick, holding on to a stick with its beak while DeLuise whirled it around at high speed. I was mesmerised – what happens if it loses its grip? Few words were minced about the sheer crappiness of the films, but you were left with a strong impression of Feldman's gentleness, and how much people liked him. He was only 49 when he died, and he hadn't been funny for a while; but the programme made you wonder whether that wasn't just a blip: maybe there were more laughs to come.