Actor and comedian.

Born: July 21, 1951; Died: August 11, 2014

Robin Williams, who has died aged 63 after apparently taking his own life, was a comedian and actor and arguably the funniest performer ever to walk the earth. Like his close friend Billy Connolly, he was seen by many as being close to comedy genius, but with that intelligence often comes a constant search for knowledge and a compulsive curiosity. And when you add this to a need to perform, to be heard, the mix can prove to be catastrophic.

The biographer Andy Dougan pointed out that Williams could not stand silences. Even when appearing in dramatic roles on stage such as Waiting For Godot, with his close friend Steve Martin, Williams had a problem with stillness. And that continual demand to fill the empty space clearly pulled at his core.

This manic energy first showed itself to the world when he arrived in 1978 as an alien in the television sitcom Happy Days. Such was the success of the guest role, the character of the space creature was recreated in Mork and Mindy, with Mork flying to Earth on an egg-shaped spacecraft, sent from the planet Ork to observe human life (and offer a morality tale).

Each week, the show allowed for Williams to perform a frenzied improv comedy riff, reminiscent of his performances on the Los Angeles comedy circuit. And it was only a matter of time before Holywood spotted his potential and the vocally-elastic Williams was launched onto a film career in which he managed to combine comedy routine, an incredible talent as a mimic, and real pathos.

He never made the leading man roles (he was perhaps seen as lacking sex appeal) but it was not surprising when he won great critical acclaim for his role in Dead Poet's Society in 1989, playing the maverick school teacher. Who could not love a teacher who gave hope and inspiration to a class, while also offering up an impersonation of John Wayne playing Shakespeare?

Williams experienced a string of film successes, with Good Morning, Vietnam in 1987, Awakenings in 1990, and the Fisher King and Hook in 1991. The nearly unbroken line of success continued with Aladdin in 1992 and Mrs Doubtfire, a 1993 comedy about a divorced father who impersonates a Scottish nanny to be closer to his children (Williams copied the voice of Scots director Bill Forsyth). And of course he won an Academy Award for Best Supporting Actor for his portrayal of Dr Sean Maguire in Good Will Hunting.

Yet, the well he drew upon for life experience seemed fairly ordinary. Born in Chicago, his mother Laura McLaurin was a former model and his father Robert a Ford Motor Company boss, although the family did move around a great deal and young Robin grew up a shy kid.

The family moved to Marin County, California, and Williams seemed to overcome his shyness through school drama. Indeed, so prodigious was his talent that he was awarded a full scholarship to the esteemed Juilliard School in New York, where one of his classmates and future close friend was the future Superman Christopher Reeve.

Throughout the eighties, Williams began to reach a wider audience with his stand-up comedy, including three HBO comedy specials. But his personal life was seldom less than complicated. In 1978, he married his first wife Valerie Velardi and they had a son Zachary. After a messy divorce, he married Marsha Garces, his son's nanny, who was several months pregnant with his child. They had two children, Zelda Rae and Cody Alan but in 2008, Ms Garces filed for divorce from Williams, citing irreconcilable differences.

The actor married his third wife, graphic designer Susan Schneider, in 2011 and they lived in Williams' house in San Francisco. His marriages however had been regularly de-railed because of his cocaine and alcohol abuse. ("Cocaine; God's way of telling you you've made too much money", he once said.)

In a newspaper interview in 2010, Williams spoke about a relapse into alcoholism. "Oh, God, you find yourself getting emotional. It breaks through your barrier, you've literally cracked the armour. And you feel really mortal." When asked if he felt happier, Williams replied; "I think so. And not afraid to be unhappy. That's OK too."

Ironically, Williams, who was fairly religious ("I'm Episcopal Church - Catholic Lite - same rituals, half the guilt"), was able to create infectious laughter wherever he went, continually uplifting souls. He loved his time in Scotland visiting Connolly at his home. Scots actor and Still Game star Gavin Mitchell met Williams on the set of the Bill Forsyth movie Being Human in 1994, and the pair stayed friends, with Mitchell visiting Williams at his home in the States several times.

"He was fantastic with the cast on set," says Mitchell. "He loved the very idea of making people laugh, and he could do it with everyone, kids, adults alike. He even made Superman laugh for the first time (when he visited Reeve in hospital).

"But it didn't matter to him whether you were famous or not. And he was extremely generous, backing the likes of actor David McGowan to go study at the Lee Strasberg Academy in New York. Robin was a very special man."

There were no professional pressures on Williams to explain why he would end his own life. A recent TV show The Crazy Ones, in which he played the dad of Sarah Michelle Gellar, was not renewed after its first season.

But he had four films in production, including the return of A Night At The Museum playing the statue of Teddy Roosevelt who comes to life at night. In April, the Hollywood Reporter said Fox Movies was developing a sequel to his 1993 hit Mrs Doubtfire.

Yet, the man who loved bicycles (he owned more than 50 of them) could not seem to stop his own mind turning over.

He was bi-polar, and those who knew him wondered if his constant searching for the laugh, the continual analysis that provided his clever satirical stand-up comedy, revealed a man who thought and cared too deeply. Perhaps he tried too hard to be the Robin Williams we wanted to see?

Even when talking about his addiction, he was compelled to be funny. In the early 1990s he said the death of a friend and the birth of his son prompted him to quit drugs: "Was it a wake-up call? Oh yeah, on a huge level. The grand jury helped too."

Last month the star who raised hundreds of thousands of dollars for charities, including Comic Relief, checked into an addiction centre in Minnesota for several weeks. But the demons did not subside. Now, his passing is being mourned the world over. Director Steven Spielberg summed up his friend precisely in the statement: "Robin was a lightning storm of comic genius."

Even President Obama was moved to write: "Robin Williams was an airman, a doctor, a genie, a nanny ... and everything in between. But he was one of a kind."

In Dead Poets Society. Williams' character inspired his students with the words: "Carpe Diem. Seize the day. Make your lives extraordinary." The silent, sad death of the huge talent makes those words all the more poignant.

He is survived by his wife, two sons and a daughter.