The death of Robin Williams has sent waves of sadness around the world. Though he was known to have recently suffered a descent into one of his recurrent bouts of depression, there was also cheering news about his agreeing to a sequel to Mrs Doubtfire to quell serious concern from half-informed fans and journalists.
His vulnerability to depression was well-known – he had talked about it frankly himself through the years – but perhaps because it was kept behind closed doors, as depression usually is, while the public continued to be treated to a persona of startling buoyancy and joie de vivre, it didn't, to the initiated, seem like a threat to the maintenance of the man.
There are few performers in the last 50 years who have had the energy and sheer force of personality to light up a live stage like Robin Williams. His stand-up act, which he seemed to summon not from memory, but from a darting, fizzing frontal lobe, was one of the wonders of the comedy world.
It was exhausting to watch him bounce around the stage, riffing on a random theme with the pace of a machine-gun. He was frenetic, but also always dazzlingly clever and astute, his intellect as formidable as his boyish chutzpah.
The term "force of nature" has become a hackneyed cliche, employed for anyone with enough character to leave an impression in a small room. But Robin Williams was the real thing; his precocious talent, the speed at which he moved and thought, the fact that, no matter how quickly his often improvised spiel flew out of his gabbling mouth, he was always belly-achingly funny, made him both intimidating and verging on heroic.
He was a human lightning rod, drawing, in both his stand-up and his films, genuine awe from his audience. But only after they'd stopped laughing. He made millions of people feel good. To lose him to depression feels like the cruellest of jokes.
It is this oxymoron which commentators have fixated on as the media take stock of Williams' shocking death from what looks like suicide at the tender age of 63. The idea of a man who didn't merely embrace life, but danced around the room with it, suddenly unable to find a chink of light bright enough to want to keep living, is incomprehensible to anyone who has not suffered depression themselves.
How could it be possible? Williams was one of the most lauded men in his profession, admired beyond measure among his colleagues and adored by his audiences.
It wasn't just the A-list success which made Robin Williams's life enviable; it was the unusual absence of surly bad behaviour, or malevolent gossip among co-workers.
For two decades his career was in constant ascendance – he gained instant fame in his 20s with sitcom Mork & Mindy, became one of America's most popular stand-up comics and starred in numerous critically acclaimed box office smashes, including Good Morning Vietnam, Dead Poets' Society, Mrs Doubtfire and Good Will Hunting, for which he won an Oscar.
But this tale of a supernova didn't come accompanied, as massive success so often does, with tales of secret awfulness on set, or falling out with cast or crew. There was a notable absence of schadenfreude among his peers in an industry which usually makes a nest of vipers look like a venue for a laid-back, bring-your-own-beer frat party.
Interviewers found themselves disarmed by Williams's warmth, wit, humility and honesty. Part of that honesty was free, unashamed talk about his periods of depression and addiction to cocaine and alcohol, but he didn't appear to mention these in order to court pity, or play the iconic Hollywood role of the sad clown. He seemed simply to be a man who was honest about his life and perhaps felt the keeping of big secrets was dangerous or deceitful.
Maybe letting the world know about his vulnerabilities was a kind of therapy, or a generous reaching out to others suffering a similar struggle. Whatever his reasons, the result was, oddly, that we tended to believe that Williams's lack of shame suggested he was dealing successfully with his demons. And that, when we saw him in another film, playing the fool, telling jokes, or even just smiling that oak-felling huge grin of his, it meant he must be okay.
In fact, the stark duality of Williams' character was apparent from an early age. Despite looking like a man who looked born to be on stage, Williams was a shy, quiet boy who only shared his genius for impersonation with his mother until he got involved with the drama club at high school.
Once revealed, however, his prodigious talent was hard to miss – he was awarded a rare place in an advanced class at the prestigious New York performing arts school Julliard when he was 22 and then offered the starring role in his own sitcom after a brief appearance on Happy Days. From 1978 to 1982, Mork was one of the most popular sitcom characters in America and around the world; there can't be many over-40s who don't remember Mork's "Nanu Nanu" sign-off. After that it was a short and inevitable step into a stand-up act, which has become legendary – he was voted 13th Greatest Stand-up of All Time in Comedy Central's 2004 poll, but many feel that was a disservice.
Then came the outstanding movie success and some of the most memorable Hollywood scenes of the last 50 years; Mrs Doubtfire waggling her well-padded fake bottom as she boogied her way through the hoovering; Aladdin's Genie launching into a series of breathtaking topical impersonations and zinging one-liners before he got down to the day job; poetry teacher Mr Keating being halted on his final departure from the classroom by a chorus of impassioned "Captain, my Captain" from his devoted, loyal students.
It is hard not to think of this last scene now without being supremely moved; the boys seem to speak for all of us, desperate to stop Williams from leaving without a gesture of our love and admiration.
And yet, as easy as Williams's career seemed to come, his personal life was blighted by periods of despair. He developed a cocaine addiction almost as soon as he developed a career, as unpalatable as the idea of the sunny-natured Mork battling with drugs may be.
The fatal overdose of his friend, comedian John Belushi, in 1982 prompted him to give up drugs and alcohol. He later said, "Cocaine is God's way of telling you're making too much money." However, in 2006, his publicist announced that "after 20 years of sobriety" he had "found himself drinking again" and checked into rehab.
Williams said later he turned to booze while filming in Alaska, from where he could see "the edge of the world" and felt alone and "afraid of everything. It's just a general all-round arggghhh. It's fearfulness and anxiety." Two years later, after 19 years of marriage, his second wife, Marsha Garces, with whom he had two children Zelda (25) and Cody (22), filed for divorce.
Journalist Decca Aitkenhead interviewed him in 2010 and described him as having a bearing which was "intensely Zen and almost mournful". Despite the film he was promoting, World's Greatest Dad, having been widely lauded as an intelligent, compelling highlight of his patchier later catalogue, he was reluctant to go through the usual PR puff and instead seemed keener to discuss his psychological troubles. However, he married graphic designer Susan Schneider in 2011 and settled into what appeared to be a happy relationship.
Depression, though, is a tyrannical and indiscriminate illness which takes little account of its victims's circumstances. Williams is said to have been a sufferer of bipolar disease, which some have suggested might explain both the high-energy mania of his comedy and the depth of his depression. Just last month he admitted himself into an addiction centre in an attempt to combat his alcoholism.
Still, the news of his death from an apparent suicide has knocked the acting world sideways, with tributes pouring in from a multitude of stars who both admired and liked him.
President Barack Obama said: "Williams arrived in our lives as an alien, but he ended up touching every element of the human spirit. He made us laugh. He made us cry. He gave his immeasurable talent freely and generously to those who needed it most, from our troops stationed abroad to the marginalised on our own streets."
Fellow wordsmith, ex-Python and film director Terry Gilliam, who directed Williams in The Fisher King, put it beautifully: "The most astonishingly funny, brilliant, profound and silly miracle of mind and spirit, has left the planet. He was a giant heart, a fireball friend, a wondrous gift from the gods. Now the selfish bastards have taken him back."
One of the most poignant responses came from actress Lisa Jakub, who played his daughter in Mrs Doubtfire and was eagerly looking forward to working with him again in the sequel.
Expressing great sadness at his death Jakub said she had "always assumed there would be some future opportunity to tell him he changed my life". There will be many actors, comedians and fans who will feel the same.
In 2010, Williams said, with a wry, not entirely approving, smile, "In America they really do mythologise people when they die."
It is impossible to imagine him avoiding that fate now.
A gilded screen career
Mork & Mindy (TV, 1978-82)
A wacky alien (Williams) comes to Earth to study its residents and the life of the woman he boards with (Pam Dawber) is never the same again
Good Morning, Vietnam (1987)
Williams plays an unorthodox and irreverent DJ, who begins to shake up things when he is assigned to the US Armed Services Radio station in Vietnam in Barry Levinson's charming comedy
Aladdin, a street urchin, accidentally meets Princess Jasmine, who is in the city undercover, in Ron Clements and John Musker's animated feature. Aladdin and Jasmine love each other, but the problem is she can only marry a prince. That's where Williams's Genie comes in
Mrs Doubtfire (1993)
After a bitter divorce, an actor (Williams), disguises himself as a female housekeeper to spend time with his children, held in custody by his former wife (Sally Field)
Good Will Hunting (1997)
Will Hunting (Matt Damon), a janitor at the Massachusetts Institute of Technology, has a gift for mathematics, but needs help from a psychologist (Williams) to find direction in his life
One Hour Photo (2002)
In a rare darker role, an employee of a one-hour photo lab (Williams) becomes obsessed with a young family, with tragic results