When the late, great Heath Ledger breathed life into the Joker, Gotham City’s most sinister villain, just over a decade ago, his depiction of the “agent of chaos” earned him universal acclaim and a posthumous Oscar as Best Supporting Actor. It also set the benchmark by which every subsequent iteration of the comedian-turned-master criminal would be measured. With those very big clown shoes needing be filled, it fell upon Joaquin Phoenix to take on Ledger’s legacy, while also facing the challenge of humanising the homicidal, ever-smiling sociopath.

When Puerto Rico-born Phoenix was first sounded about the role, he was understandably reluctant to sport the rictus grin, largely on account of Ledger’s performance being widely regarded as definitive. He was also a little deterred by the character’s grotesque comic book back-story, worrying that it lacked any real-life resonance.

Despite such concerns, Joker director to be, Todd Phillips, convinced him to don the mantle, reassuring the actor that his take on the character had been created with him specifically in mind. Ultimately, Phoenix – a 30-year stage and screen veteran – became convinced it was the right thing to do as he immersed himself in the role, even to the point where he suggested the possibility of a second cinematic outing for the character in the second or third week of shooting.

Recalling this, he says: “Very early on, I was like: ‘Todd, can you start working on a sequel? There’s way too much to explore.’ While it was kind of largely in jest, it wasn’t wholly so.”

Indeed, a sequel may now be just what Warner Brothers – the studio behind the movie – is now hoping for, given that the film took more than US$1.1 billion after opening to an eight-minute standing ovation at the Venice Film Festival. It’s only the 44th movie ever to achieve a nine figure gross, while also being the biggest hit of Phoenix’s career.

Beyond its box office success, Phoenix’s performance as the damaged clown also sparked wide debate about both mental health and the roots of societal violence. Assessing the wider impact of the movie, the actor says: “It’s not the box office receipts, but the reception that’s been truly vindicating. I now get emails from people telling me that it made them look at their schizophrenic sister in a different way. Ultimately, the movie is about the power of kindness and the lack of empathy in the world, and the audience seems to have picked up on that.”

It is also fair to say that audiences worldwide have also picked up on just how compelling Phoenix can be on screen. Though his career stretches back some three decades, he has never been viewed as high in the Hollywood pantheon of all-time greats. Despite never being a darling of the media, though, he has actually appeared in some of the most critically acclaimed films of recent years, with his contribution frequently being viewed as crucial.

Something of a child protégé in acting terms, he and his four siblings were ‘discovered’ by Iris Burton, one of Hollywood’s leading agents. With his talents soon apparent to casting directors, he swiftly graduated to supporting roles, most notably in To Die For (1995), a Nicole Kidman vehicle where his performance as a lustful teenager proved a true scene-stealer.

His big breakthrough, however, came in 2000 when he took on the role of Commodus in Gladiator, Ridley Scott’s Roman epic. His first outing as a Big Bad also earned him his first Oscar nomination (as Best Supporting Actor). Since then, he has been nominated for two further Oscars – one for playing musician Johnny Cash in Walk the Line (2005) and one for his role as war veteran Freddie Quell in The Master (2012). So far, none of his nominations have converted into actual wins, but this may well change with his bravado performance as the Joker seen as sure to secure him the Best Actor award later this year.

His unusual film choices to date, however, can be better understood through the filter of his equally unconventional life. Born Joaquin Rafael Bottom in Puerto Rica in October 1974, his parents – John Lee and Arlyn – were American citizens and members of the Children of God, a controversial California-based extremist Christian cult. Ultimately rejecting the cult’s teachings, the family relocated to Los Angeles, where they reinvented themselves under a new surname – Phoenix, the bird that, in classical Greek mythology, rose from its own ashes.

With his mother working as a secretary for NBC, one of the biggest TV networks in the US, it wasn’t long before the junior members of the Phoenix family found themselves competing in a series of televised talent contests. It was then that young Joaquin adopted the stage name Leaf Phoenix, which he continued to be credited under until he was 15 and reverted to his true name.

In addition to his penchant for alternative names, he has also been widely seen as favouring an alternative lifestyle. A vegan from the age of three, he has also been an almost lifelong supporter of PETA, the anti-animal cruelty charity. Well before such concerns went mainstream, he was at the very forefront of the movement, frequently using his fame to raise awareness of such evils as dog leather and the poor treatment of circus animals.

Announcing him as PETA Person of the Year for 2019, Ingrid Newkirk, the organisation’s president, paid tribute to the actor, saying: “Joaquin Phoenix never misses an opportunity to turn the spotlight away from himself and onto the plight of animals, while setting a great example by truly walking the vegan walk.”

Clearly a performer bold enough to make unconventional career moves, he once went public with his determination to quit Tinseltown in favour of making it big in hip-hop. That, however, ultimately proved to be a role he was playing in I’m Still Here, a 2010 ‘mockumentary’ that purported to chronicle the actor’s spoof sabbatical, right from the announcement of his ‘retirement’ to his debut before a clearly bemused audience of hardcore hip-hop fans.

While the film got a decidedly mixed reactions, it also kept many guessing as to just which elements of it were heartfelt and which were merely scripted provocation. In many ways, it’s this very ambiguity that lies at the core of Phoenix’s best performances, with the will there / won’t there be a Joker 2 just the latest manifestation of his ability to ensure audiences never quite know what is coming next.