When Sir Ronald Harwood criticised the casting of Glenda Jackson as King Lear at the Old Vic last year, he was subjected to a storm of righteous rage. “I’ve never had such a lot of emails ,” he says. And they weren’t friendly.

But he was unswayed from his firmly held view that it is “monstrous to destroy the playwright’s intention” by casting a female in a role written specifically for a male.

Secure in the status of more than half-a-century’s work for stage and screen, Harwood is not a man to go with the flow of theatrical trends, especially of the polemical kind. “I don’t want to be preached at,” he says, settling into an armchair in his elegant Chelsea home, a cigarette between his fingers. “I want to make up my own mind.”

Some say that his favouring of traditional, classically structured plays over the political or experimental kind could be what lies behind this most distinguished and prolific of dramatists never having had a play put on at the National Theatre.

But, ignored though he may be by the resolutely fashionable theatrical establishment, Harwood has certainly collected honours aplenty, including being made a knight and CBE, and picking up an Academy Award, Bafta, teaching post at Oxford, and any number of honorary fellowships and degrees.

Now there is a biography, Speak Well of Me, by W. Sydney Robinson — though, given Robinson’s sometimes wincingly florid writing, this is hardly as gleaming a tribute as those above.

Especially since, despite placing his subject amid the “grassy uplands of literary greatness”, where “all of these peaks seemed to tremble before him”, Sir Ronald’s biographer is not above the occasional unflattering description.

For example, after winning an Oscar, Ronald Harwood was, according to the egregious Mr Robinson, ready to dish out a “dollop of that hard-earned smugness which is his own”. And, it seems, the theatre, for Harwood, is “a vehicle for self-aggrandisement” wherein he carries out his research “with the discernment of an inebriate” while feeding his “insatiable appetite for fame”.

None of this seems remotely to fit the friendly, funny and unassuming person sitting across from me in that pleasant Chelsea parlour, happily smoking as he looks back over his life and career.

Harwood was born Ronald Horwitz in 1934 in Cape Town. He grew up in what he recalls as a “very Jewish, South African home”, which he left at 17 to try his luck as an actor in London.

“My father, an immigrant from Lithuania who spoke English with a very heavy accent, was a rather sad man. He never really made a living — and my mother took it out on him. She resented that she had to go out to work.

“My memory of her is very strong. She followed me to England” — where, he says, his Jewish identity has remained strong and constant: “The Jews, I believe, are the yeast of mankind.”

There is no shortage of Jewish characters and themes across Harwood’s work, from the TV plays The Barber of Stamford Hill and Take a Fellow Like Me through the brilliant stage dramas Taking Sides and Collaboration to the film, The Pianist, directed by Roman Polanski, with whom Harwood enjoyed not just a “very good working relationship” but a genuine friendship — “I still talk to him often.”

The Pianist is based upon Harwood’s adaptation of the autobiography of Wladyslaw Szpilman, a Polish Jewish musician who, incredibly, survived the Second World War in Warsaw. Szpilman’s story is similar to Polanski’s own. He, too, managed to survive the war in unlikely circumstances in Poland.

But one subject absent from the conversations between Polanski and Harwood was the deadly fate of the rest of Polanski’s family. Another was the alleged rape of a 13-year-old girl by Polanski, which prevents him from entering America.

This is not to say that Harwood shies away from serious or moral issues. Far from it, as vividly demonstrated by both Collaboration — about the complex relationship between the German composer Richard Strauss and the Jewish writer Stefan Zweig — and Taking Sides — about the “denazification” of the conductor Wilhelm Furtwangler by a US army officer. Both are true to Harwood’s principles: “I let the audience make up its mind. I don’t lecture. My theory regarding theatre is that it should be entertaining and if it has any strong moral purpose, it should be concealed. No preaching!

“Always at the back of my mind, when writing about a moral dilemma is the example of apartheid and the question: ‘How would I know how I would have behaved?’ Taking Sides was about that. If you live in a dictatorship, and you have a threat to your family and to yourself, it’s very difficult to behave bravely. Very few people did. Most people just accepted apartheid. I didn’t behave well at all. I behaved well when I got to England, when I was out of it, but when I was there I accepted it. Many people claim they questioned it but I doubt it.”

The Pianist, in 2003, brought full recognition, in the shape of an Oscar, of Harwood’s specialist skill as a screen adapter. He had already been nominated for the film of his own play, The Dresser, and would be again for his adaptation of The Diving Bell and the Butterfly, Jean-Dominique Bauby’s remarkable account of the locked-in syndrome that left him able to communicate only by blinking his left eye. No Oscar this time but it did win a Bafta for Sir Ronald.

However, The Dresser is probably Harwood’s most celebrated creation, as play and film. Drawn from his own experience of working as a dresser to the legendary actor-manager Donald Wolfit, whose biography Harwood also wrote, it is a loving tribute to the world of theatre, in which he has been active since coming to London as a raw, would-be actor.

“But I was such a bad actor, I could never have made a living. Now, I love writing.

“I didn’t know I could do it until I started when I got married in 1959” (to Natasha Riehle, a descendant of a grand Russian family, who died four years ago).

Since then, his output has been astonishing, not just of plays and screenplays but also novels, and the Wolfit biography. And he is currently working on a screenplay of Terence Rattigan’s Man and Boy, which will star David Suchet.

A list of Harwood’s friends and colleagues would read like a Who’s Who, from Harold Pinter to J B Priestley, Anthony Hopkins to Dustin Hoffman, not to mention his cousin and fellow “Sir”, Antony Sher. And, while this knight of the realm and member of both the MCC and the Garrick club might seem so terribly English, when asked which was more exciting, the Oscar or the knighthood, he is unhesitating:

“The knighthood. Because my mother would have been so proud. This is a Jewish boy from Cape Town.”

‘Speak Well of Me’, by W. Sydney Robinson, is published by Oberon Books