The towering figure of the Australian theatre - he is both incredibly tall and was a mainstay of the mainstage for 50 years - concedes that his quest to get it right and depict as accurately as he could the drama he saw around him was not a flattering, or pleasant process, for everyone involved. He was, he says, "a little more ruthless than I should have been in borrowing from life".

"I was a bit cavalier in the early stages of my career. Luckily, most of them sensed that there was - as well as the social satire and criticism - an affection and warmth towards even my flawed characters, that meant I didn't hate them," Williamson tells me, in the reflective mood that comes with talking about a new memoir.

Home Truths, published this week, surveys the life and times of Australia's most-performed playwright. It is an arc which took him from designing a handbrake that did not work at Holden's Fishermans Bend plant to becoming Australia's most prominent playwright, with a string of plays that are frequently revived, and recognisable as household names: The Removalists, Don's Party, Emerald City, The Club, Travelling North and so on and so on for five decades.

Williamson has battled critics and retained strong audiences, before retiring, he says, after his last shows in 2020, which snuck in seasons before the theatre world and a global pandemic met on an inevitable collision course.

Williamson was always interested in social realism, putting the real world on stage and pulling it apart. He took from his own life, and the life of his friends, to do it, crafting characters that cut too close to the bone for some. He has brought the same eye to his memoir, where there's little gilding around the edges. "I'm sometimes surprised by how some aspects of some people's characters that are glaringly obvious to the rest of the world are not glaringly obvious to them," Williamson says.

Williamson's new memoir is not a particularly flattering portrait of the man himself. The good is certainly mixed in with the bad. In part, it can feel as if he is at great pains to lay out his own flaws: the rough patches of his marriage, the dogged pursuit of success, and the extreme levels of work that ended up exacerbating Williamson's heart troubles. But he says he'd probably do all that work again, and avoid some of the mistakes: "I was driven not so much by fame and fortune, I like to think, but by the addiction of actually getting a work on stage, going through that exciting process of rehearsal and then the even more exciting process of the first audience to see whether I'd written something that was going to connect. And when it did, the adrenaline buzz - it's like a junkie. You go, 'Wow. I want that experience again.'"

Williamson says he just can't stand memoirs that are puff pieces for their authors. "I keep saying, 'Be effing honest with yourself'," he says. "So I was determined if I was going to write this - and I wasn't going to write it for a long while, until I felt I can handle it - I was determined not to evade my own shortcomings. It would have been unfair of me to probe other people's shortcomings and leave my own aside. So I, you know, it was just anathema to me."

Williamson was born in Melbourne in 1942, to parents Keith and Elvie, who spent a married lifetime bickering. His mother, Williamson writes, "was naturally disposed to assume that everyone was an enemy until proven otherwise" and his father "was essentially a good and tolerant human being". It was a natural set up for dramatic conflict, the kind Williamson says he was always fascinated by as a dramatist. "In a sense, as Kristin, my wife, pointed out, I grew up with theatre around me. Every day without actually categorising as such, it was just ongoing marital warfare. Not of the physical kind, but of the psychological kind," Williamson says.

"So I had a deep need to understand why people fought all the time and what were those sources of conflicts. Did life have to be like this? What was I destined to - endure a lifetime of continuing drama? I hoped not, but it was certainly going on in the house, so, yes, everyday life around me, and the rivalry between relatives - my aunt and my mother, her continual political scheming."

The Williamsons moved to Bairnsdale, where Keith took a job managing a bank. Williamson did well in the country high school, but writes he had some difficulty suppressing his ego and dumbing himself down. "My insufferable arrogance earned me the derisive nickname 'Genius' and I veered close to being socially ostracised," he writes. But Williamson's introduction to Shakespeare's Julius Caesar and Macbeth in third and fourth forms opened the door to a "thrilling new vista where the answers to [his] urgent curiosity about human behaviour lay waiting to be discovered". But it was Williamson's aptitude for maths that diverted him. The pressure was on to take a real degree, especially so after he returned to Melbourne.

"I had no idea what I wanted to be, except I knew vaguely that I wanted to be something creative, and hopefully I wanted to write. But at the time when I was growing up, the chances of that actually leading to earning a living were so remote that I didn't even dare mention it to anyone in case they thought I was crazy," Williamson says.

Williamson went on to become the first graduate in mechanical engineering from Monash University in 1965, after failing too many units at Melbourne University, where his taste for theatre was encouraged in contributions to the Engineers' Revue. "I was now qualified to practise in a profession concerned with all things mechanical, but still unable to diagnose or repair even the simplest problem under the bonnet of my car," he writes. That career - which included a stint teaching at Swinburne after a fairly unsuccessful run at General Motors Holden, where he read Chekov under the desk - was short.

"I steered myself towards an MA Prelim in psychology once I was teaching and that was far more satisfying and I did far better at that than I did at the engineering, and I was scheduled to go on and do postgraduate in psychology when the writing took off at the same time, but as I said in the book, it was virtually the same activity. I was a social psychologist on stage in the way that I wanted to explore human nature academically."

Also in 1965, Williamson married Carol Cranby, then a high-school art teacher who hoped to become a full-time artist. It was a difficult marriage almost from the start. "The reception was held at Carol's father's place and all I can remember is that I drank too much and danced too long with Carol's sexy sister, Toni, before mentally slapping myself on the wrist and telling myself that all that was over. I was a married man now," Williamson writes of his first wedding night.

It would be impossible to fault Williamson for not being brutally honest. Williamson's memoir does not hide the ambition he had to be a playwright, at the expense of home life. His criticisms of Carol are matched by the criticisms he has for himself: "I became an insufferable husband." On a 1970 Christmas holiday, Williamson and Carol were spending some time in a caravan with their young daughter, Rebecca, at Rosebud, on Victoria's Mornington Peninsula. "When I took out my clipboard and foolscap sheets ... Carol wasn't amused. We'd come on holiday to get away from all that. I was supposed to rock my beautiful young daughter in her cradle and sing lullabies. I tried my best, but there's nothing more ferociously obsessive than a young writer on what he believes is the cusp of national recognition," Williamson writes. (The marriage to Carol wouldn't last; he would eventually marry Kristin Green after their relationship grew on the set of The Removalists, but Williamson is upfront that this relationship, which has endured, was not smooth sailing all the way through either.)

Williamson was working that Christmas holiday on what became Don's Party, the 1971 play set on the night of the 1969 federal election, when Australia came close to throwing off two decades of conservative governments but didn't quite make it. It shocked audiences, though Williamson knew it was based, in part, on the parties he and Carol had held in their Bundoora clinker-brick veneer home. The male chauvinism and perceived immorality were quite a way from the English provincial stuff which Williamson says dominated Australian stages at the time.

"I didn't enjoy being an enfant terrible. I just wanted to say, 'Look, this is the Australia I know and have come to understand,' and shocked by myself in some respects, but also I delight in its energy. I wasn't uncritical of Australian society. In fact, The Removalists was mistakenly thought to be a searing indictment of police brutality by certain Melbourne aficionados, but in fact it was a very dark protest against the worst aspects of Australian masculinity. So my work wasn't totally celebrating this culture I was discovering. It was highly critical on one level and it was celebrating the energy and rawness on another. So I had a very ambivalent attitude to what I was writing, I just wanted to get it right," Williamson says.

Critics take up plenty of Williamson's time - or at least they did. He seems to have mellowed a bit now. However, it's hard not to see this as some kind of obsession from a man who never had trouble drawing an audience. Before Money and Friends opened in 1991 - which centres on a group of Palm Beach residents grappling with the question: will friends stump up cash to help friends? - he faxed his "most savage critics", asking for the play to be assessed for what it was, admitting he had not "tackled the plight of the unemployed, the drug addicted, the ethnic minorities or the working class. Nor had I tackled many social issues of inequality and fairness". Some critics were outraged by this intervention. Did it matter? Williamson writes the play took record takings at the box office and toured internationally; it was even adapted into a Polish telemovie. Clearly, a few hundred words in the papers didn't hurt it that much.

Williamson tells me the story of Dostoyevsky, the Russian novelist, and his obsession with one critic from the Ukraine who overshadowed the otherwise good reception to the novelist's work. Williamson says he did too much of that himself: more than half the notices, in scrapbooks kept by his wife, Kristin, are actually very positive.

"But I obsessed about the ones that weren't, and spent far too much of my life doing that. There was a critical resistance to my work, I think for two main reasons, i.e., yes, it drew audiences, and that automatically makes it suspect as populist or downmarket or something. I never believed my work was that. I believed it was a complex examination of complex human social behaviour, and I felt it was unfair that because people came it was assumed to be lowest common denominator, which it never was," Williamson says.

"And secondly, from the 80s, there was an increased - and justified - call for other voices than middle-class Anglo-Celts, and other cultures, to be represented on our stages. And I understood that and agreed with it, but in a sense I was sort of blamed for keeping these new voices off the stages when there was nothing of the sort."

There is something remarkable about Williamson's career. I'm not so certain anyone could replicate it today. Even reading about the path from engineer to playwright to very successful playwright to playwright who lives with a harbour view in Sydney seems to be fanciful in 2021. Sure, there would have been scores of failed playwrights in Williamson's time, too - every Sydney playwright threw their typewriter into the harbour in despair, a friend told Williamson, after Don's Party opened there. But could a playwright now hope to have a mainstage work produced every year for 50 years now? Never mind Williamson keeping people off stages, is there space to get up there for anyone toiling away now in the small theatres and university revues? What hope does the next mechanical engineer looking for a creative path have?

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The struggle to get original new work onto main theatre stages might well be tougher now, Williamson agrees. "The number of original new Australian plays going on our main stages is not nearly as many as I think there should be. Yes, it is harder for someone writing exciting work in our smaller theatres - like Griffin [in Sydney] - to get that work seen on our main stages, on our state-subsidised stages," he says. Williamson puts blame squarely at the feet of conservative governments - with their distaste for the arts, the ABC and academia generating too many uncomfortable ideas - for cutting into arts funding over the years, forcing the state theatre companies to think more commercially and take fewer risks. "The chances of the arts returning to a flourishing level through increased government aid is pretty small. So I think we're stuck with that problem," he says.

So the days of big straight dramas in 1000-seat theatres? That's now untenable, Williamson says. "I think some of the best drama now is not in film, it's streaming and cable quality television. So, yes, the theatre has got enormous competition now from really top-level drama that's readily available and that's perhaps why there's a move towards smaller theatres," he says. Little wonder then that Williamson's last play, Family Values, premiered last year at the Stables Theatre in Sydney, a Darlinghurst venue with only 105 seats. (The show made it to Canberra, one of the last productions staged here before the pandemic hit.)

But Williamson is hopeful that the theatre will endure - especially after COVID-19 subsides and it's safe again to get together as a community in the theatre, a unique experience. "Well, theatre will be kept alive by two things. People really want to enjoy an experience together, they can go to the cinema, but there are flat creatures on the screen that aren't live. The real community experience is a small 300-seater with a good play and an audience that's viscerally responding all around you," Williamson says. "That's an experience that only the theatre can offer."

After all, that's the kind of human drama we all know and want to understand, even if it doesn't cast a very flattering light.

This story appeared in Panorama, The Canberra Times' Saturday magazine of arts and culture. Why not try our weekend bundle, with the weekend papers delivered and a digital subscription through the week?