He was an electrifying Hamlet, the best ever Coriolanus and a wonderfully chaotic King Lear, a role he played for Terry Hands at Theatre Clwyd, Mold, over ten years ago, his last performance.
His name cropped up last year when Douglas Hodge played Bill Maitland in Inadmissible Evidence at the Donmar. The role was written by John Osborne for Williamson, and he introduced it in 1964, reprising it some years later when he was more the right sort of age. No one did rancour, bitterness or spiritual failure better than he.
The Lear was all over the place, but full of brilliance and great shafts of pathos. Many of the speeches were cut to shreds and delivered in the wrong order. But it really didn't matter. You just knew you were in the presence of true greatness.
I was worried about the trip. Getting to Mold was always a nightmare, but I knew I'd taken the the right train connection at Chester when I spotted half a jazz band at the other end of my compartment.
The happy band of musos, who included the film critic and sometime theatre critic of the Daily Express, Ian Christie, were only going to one place: their mate Nicol's first night.
After the performance, I filed a review from the theatre's office and waited for a taxi back to my hotel. The party was already in full swing and I'll never forget the look on Williamson's face as he stormed from the auditorium into the bar, ready for anything.
He'd just played the greatest role on the dramatic stage but was now getting down to the night's serious business: the party after. Terry Hands told me that he'd cancelled the next night's performance as no-one, least of all Nicol, would be in any shape to do it.
The stories of Williamson walking off the stage, falling out with his colleagues and behaving badly are legion. But his emotional fragility was all part of his talent, which ruthlessly excised anything resembling sweetness or sentimentality and carved out his stage personality with a scalpel.
His Ophelia was Marianne Faithfull, his Lady Macbeth Helen Mirren, his wife the beautiful blonde actress Jill Townsend, whom he cast as Yelena in his own very fine RSC production of Uncle Vanya in The Other Place in 1975.
By the end of the 1970s he had divorced Jill and was living mostly in Amsterdam, though there were reported sightings of him in various North London pubs.
I have no idea if he was a recluse or not. I do know that, on his day, he was the most exciting actor I ever saw, if only because he radiated such danger, such risk.
He was in my first experience of Waiting For Godot in the first major London revival and nothing in the play seemed difficult or inexplicable.
I heard the news on my way to see The Taming of the Shrew in Stratford-upon-Avon last night and was immediately downcast, unaccountably upset.
It's a mark of how wonderful Lucy Bailey's production is that I had cheered up no end by the end of the performance. The show is full of vivacity, rudery, irreverence and aggressive high spirits. A fitting tribute, indeed, to a very special actor.