Dennis Potter’s legendary six-part TV series ripped up Sunday nights back in 1986, long enough ago for its reputation to have grown out of all proportion. When it was finally released on DVD in 2002, I pressed Play in the sinking certainty it couldn’t possibly be as good as I remembered, to discover not only that every frame of The Singing Detective – the curling blue smoke, the drab grey hospital light, the livid red skin, the green, stirring mystery of a British forest canopy in the afternoon – had been etched into my memory, but also that it was all even better, richer, stranger, wider and deeper than I’d suspected.

It’s the story of a man who was once a writer, bedridden in hospital by chronic psoriasis; and it remains the most acute picture of what life in a British hospital is like, even though it was made when you were still allowed to smoke in your ward bed. Hideously imprisoned by his own burning flesh, and trying to avoid his suspicion that the disease is an outward manifestation of his own moral sickness, he spends his days and nights trying to work out the plot of a book – a murky British pulp noir, labouring heavily under the American influence, about spies, sex and murder in the blacked-out London of World War Two – which leads him into the awful business of trying to work out the plot of his own life.

Assaulted by fever and drugs, his existence becomes a cracked, musical kaleidoscope as reality, perception, memory, fantasy, sex and guilt mingle and merge. It’s profoundly moving, wrenchingly painful – and, it should be stressed, often wickedly funny.

It might be the best work by all involved: as the protagonist, the knowingly, shabbily, cornily-named Philip E Marlow, Michael Gambon is witty, nostalgic, sensitive, aching, anguished, mean-spirited and desperately miserable, a detailed, perfectly-judged portrayal of a soul in everyday agony. Rifling his own film noir memories, director Jon Amiel finds images to complement Potter’s vision in a manner that almost makes you forget to wish that David Lynch had been given the job. And, in this most startling collage of social, cultural and, above all, astonishingly personal musings, Potter writes the piece all the staggering scripts he wrote before pointed toward, and to which the arresting projects he tackled afterwards couldn’t quite live up. They made a film of this, starring Robert Downey Jr. There’s no need to ever watch it. No shame in saying it again: a masterpiece.