But even his moans are tinged with laughter, and it doesn't take much to get him shooting off in some wonderful satirical direction with a funny voice or a scathing critique. One of his favourite cries, when Irving Wardle was the Times critic, was, "How's old Irving these days? Still fidgeting away on the aisle in his anorak, is he? A severe case of anoraksia nervosa, I always thought!"
This gift for sharp, witty brilliance, along with many other gifts, was much on display in last weekend's BBC Arena profile. Miller's virtues were proclaimed by old school friends (neurologist Oliver Sacks and bookseller Eric Korn) and professional colleagues (Penelope Wilton, Roger Norrington and Eric Idle), and there were illuminating passages on his never-bettered Alice in Wonderland television film, his Horizon programme with a Parkinson's sufferer, and how he got Olivier to hop about like Hitler when his Shylock first learned about Antonio's losses at sea.
But where was Alan Bennett? These oldest of friends and closest of neighbours did have a falling out some time ago, and Bennett wouldn't have celebrated or even smiled much at Miller's acceptance of a knighthood, but I can't imagine they are no longer sitting in each others' Gloucester Crescent kitchens every other day.
Maybe we'll learn more about this when Kate Bassett's long-awaited biography is finally published. Meanwhile, the TV film was pretty good and allowed plenty of time for Miller to expatiate on his pet enthusiasms: the "after-life" of art, his own delight in "found" objects and abstract art, neurological analysis of acting, wandering around markets and museums in Florence, talking.
Even at the age of 77, and only slightly stooping, there's no containing him. And he still wears jeans without looking ridiculous, blending them with his perennial smart casual old-style Brooks Brothers look of sports jackets, corduroy and dark blue sweaters.
With a new Long Day's Journey Into Night opening next week, it was fascinating to revisit his 1986 production which featured Jack Lemmon and Kevin Spacey, and which used overlapping dialogue not just to speed up the play, but also to emphasise the fact that these family rows were a daily ritual that had been going on for years.
As so often with Miller, he started with an antagonistic stance towards the work -- he was having nothing to do with its status as the American theatre's classic "Greek" tragedy -- and found ways of feeding that anatgonism into a revelatory creative process.
Oddly, while the Long Day's Journey segment was on the screen, the soundtrack of Leonard Bernstein's Candide was playing, unexplained (Miller did in fact direct the musical, two years later, for Scottish Opera, and at the Old Vic).
But otherwise this was an almost perfect film, marvellously conveying the richness of Miller's life and intellect. There's absolutely no-one else like him in our theatre and that's partly because Miller doesn't really "belong" in the theatre; he swoops on it with all the freshness and spontaneity of an anarchic maverick, spreading ideas and joy like a subversive visiting professor.
He talked a lot in the film about "yielding" to show business, as though he'd been diverted from his true path in medicine and neuropsychology by lines of flirtatious chorines in fishnet tights and "Larry" Olivier giving him a toybox.
But Oliver Sacks put it best in saying that Miller had, in effect, never left medicine, but had been compelled to go in many directions at once by the sheer vivacity of his outlook and interests.
One of the things Miller is most brilliant at, almost uniquely, is transferring a play or an opera to another period, perhaps the one in which it was actually written as opposed to the one in which it was set by the writer or composer.
And he's also been inspirational in moving operas into a modern setting that clicks perfectly all the way through. The best of these were at the ENO: the 1940s war-time Tosca, the "Little Italy" Rigoletto (in which the duke hit the juke-box) and the black and white 1920s The Mikado in which, as the Arena film aptly illustrated, the Mikado's great entrance scene was almost entirely lifted from the Marx Brothers' Duck Soup; Miller's starting point was, "I wanted nothing at all to do with all that Japanese rubbish."
These productions came to mind again as, earlier this week, I watched the Young Vic revival of Patrick Marber's brilliant, Miller-esque transposition of Strindberg's Miss Julie from a steamy Swedish midsummer's revel to the night of the Labour Party election landslide in 1945.
Everything in After Miss Julie clicks perfectly into place in Natalie Abrahami's production, and Natalie Dormer and Kieran Bew carry a weight of class-imbued sexual warfare into their scenes of humiliation and control that casts a nostalgic/prophetic shadow over the whole post-war era.
And then you think back to those classic Miller productions at the Old Vic twenty years ago -- Racine's Andromache, Chapman's Bussy D'Ambois, the Eric Porter King Lear, Candide, Corneille's The Liar, and the designs of Richard Hudson, and the other wonderful shows by Richard Jones -- and, yes, they were all much more exciting and interesting than anything done on Spacey's watch -- until, I reckon, the very latest, The Duchess of Malfi.
Which is not to decry the terrific revival of Michael Frayn's Noises Off, which transferred triumphantly to the Novello last night. But we already knew Noises Off was a treasurable play. No great surprises there, and no great challenge (except, of course, to the actors).
And no resting on laurels, either: not only has director Lindsay Posner fine-tuned his own production to a very high degree of delirious efficiency; Michael Frayn brought along the play's previous directors, Michael Blakemore and Jeremy Sams, to sit in the first night stalls and ponder what might still be done to tidy up the always slightly unsatisfactory third act. Perhaps he should call up Jonathan Miller, too.