It is his fingers I will remember. Longer than they had any right to be, they were both brutish and graceful, as capable of wringing a neck as of drawing an elegant shape upon the air. As Krapp, in Beckett’s monologue, Krapp’s Last Tape, keeping a surreptitious eye on the script that, from my upper-circle seat, I could see clearly open on the table before him, he let one finger drag slowly along the carving of the desk’s edge, as if playing a guiro.

Elisabeth Frink once made an etching of Michael Gambon as Antony (Helen Mirren was Cleopatra), and let his enormous hands become the largest thing in the picture, dangling at its centre with nails as large as eyes. Frink was the right artist: Gambon’s was a face carved and hewn rather than born or made, comparable, in its delicate bulk, to one of her monumental male heads.

Contradiction was perhaps the essence of his greatness, and he played upon it, hiding an evident seriousness and intellect, to say nothing of prowess at classical guitar and his crafting of replica antique weaponry, beneath the persona of one who didn’t really know what this acting lark was all about. He did, and worked at it (as his co-stars testify) with technique and determination. Much has been written about his great outings, in Dennis Potter and Stephen Poliakoff on television, or in Brecht, Miller and Ayckbourn on stage.

I wish his role as the clockmaker John Harrison, in Charles Sturridge’s Longitude, had been more praised. He was never better, and his were fingers that could easily have built maritime machines of such delicate complexity. When he lost his temper at the intransigent Board of Longitude, the power he conjured (vocal, emotional, physical) burned from the screen. (Cleopatra, on Antony: ‘But when he meant to quail and shake the orb, he was as rattling thunder.’) In a scene with Andrew Scott, during which Harrison is tempted to abandon his life’s ambition, the tears rolled down his face, and a beleaguered soul shone through basset-hound eyes. He revealed afterwards that Sturridge, without saying what was wrong, made him do take after take after take, the two of them locked in a silent battle of wills that renders the scene red raw.

Temper, commingled with humour, is part of the Gambon mythology. Any follower of his will know about the whoopie cushions on the Potter set (Harry, not Dennis); the racing on Top Gear; or the time he told a journalist that he had given up homosexuality because it brought tears to his eyes. Richard Eyre’s diaries record his storming from the stage in David Hare’s Skylight, raging and cursing like any Lear. His Lear was before I was born, but how I wish I had seen it, a performance for which he rehearsed by staring at gorillas in the local zoo, where he found Antony Sher, building his take on the Fool by sketching monkeys. Their Lear-Fool routines were staged as a vaudeville double-act before a front-cloth, with Sher sporting a red nose and Gambon whispering obscenities to him under his breath.

Twice I glimpsed him off the stage. The first time he was smoking outside a Jermyn Street restaurant, preparing for Beckett’s All That Fall at the theatre next door; the second, stalking up Shaftesbury Avenue after a performance of Harold Pinter’s No Man’s Land. I ran after him with the programme, and joined a small queue of autograph-hunters sporting Potter memorabilia. Had they seen the Pinter, he asked, cigarette in mouth. They had not. ‘Fucking hell’, he growled, his growl as loud as another’s shout, and stormed off.

Most clearly etched on my memory is his long-awaited outing as Falstaff, in the two parts of Shakespeare’s Henry IV, directed by Nicholas Hytner at the National Theatre. I saw it twice, at the beginning and end of its run, and by the last weeks critics and audiences had decided it was not quite Gambon’s finest hour. The clarity and sense of the lines were being eaten up by layers of beard and fatsuit, and – perhaps – by the early fadings of memory that soon enough led him to give up stage work. Insecurity (which may have been the key to Gambon’s triumphs and failures) led to indulgence: on my second visit, much stage business had been added, including a scene in which he managed to pee up a tree, reaching its topmost branches.

But at an early preview, promise was in the air, and he conjured magic. The life-force and humour of Falstaff one could take for granted; it was his sadness, his chimes-at-midnight mortality that lingered, as when, rejected by Hal – ‘I know thee not, old man’ – his enormous body seemed to sag, deflate, and then fold in half.

Earlier in the plays, Falstaff meets the prostitute Doll Tearsheet.

‘I am old, I am old,’ he told her.

‘I love thee better than I love e’er a scurvy young boy of them all,’ Doll replied, and meant it, because, with Gambon, she couldn’t not.

In my memory, which may have played tricks, Doll sang while sitting on his lap. My seat was at the far side of the auditorium and I could see, as the rest of the audience could not, that he was running a long finger, full of longing, down her back. There was no lechery in it. It was something one might do to a cat. It allotted her, a prostitute, dignity, in being touched with affection rather than lust.

‘It grows late,’ said Falstaff, said Gambon. ‘We’ll to bed. Thou’lt forget me when I am gone.’

No, Michael Gambon was unforgettable, a great actor.