Robin Williams documentary: HBO releases emotional first trailer

'You're only given a little spark of madness and if you lose that, you're nothing'

Robin Williams was one of the greatest comics of a generation, making audiences around the world laugh for hours on end.

Behind the curtain, though, Williams fought many personal battles, something the actor rarely spoke about publicly.

Robin Williams: Come Inside My Mind, which debuted earlier this year at Sundance, explores all aspects of his life, featuring rare footage of the comic alongside new interviews with those close to him.

"You're only given a little spark of madness and if you lose that, you're nothing," Williams says during the first trailer for the HBO documentary.

Steve Martin also makes an appearance in the clip, saying: "He was really comfortable onstage. Offstage, I just felt he was holding himself together." Watch above.

Williams took his own life in 2014, aged 63. For confidential support call the Samaritans in the UK on 08457 90 90 90, visit a local Samaritans branch or click here for details.