Nick Broomfield's special subject is the lives of the rich, famous and dead. He seems to have been making tell-all documentaries since Adam bit the apple. The subjects of his first films were usually alive: actor/comedian Lily Tomlin; the South African racist Eugene Terre'Blanche; and in 1992, the serial killer Aileen Wuornos. He has a talent for getting under the skin of his subjects - or those left behind when the subject crashes and burns, as in Kurt & Courtney, his film about the death of Kurt Cobain, or Biggie and Tupac (2002).

This film is different, because it's made from afar. He takes us through the sharp rise and spectacular fall of the late Whitney Houston, a singer with a monstrous talent and none of the tools she needed to cope with success. It's clear he thinks many of the people around her loved her - and that some of those closest to her did not love her enough.

Houston was found unconscious and submerged in her bathtub at the Beverley Hilton in Los Angeles on the afternoon of February 11, 2012. She was 48. The coroner cited a heart condition and cocaine use as contributing to her death. In the film, an unidentified voice tells it differently: "I know Whitney Houston actually died from a broken heart."

There are so many people willing to talk to Broomfield that it is difficult to sort out where he did not receive co-operation. He has said in interviews that her estate, which means her family, tried to stop his film with lawsuits and pressure on her friends.

Kevin Macdonald (Marley) announced last year that he was making an authorised film. Broomfield's is very much the unauthorised version, containing footage of two people he claims the family would prefer not to mention - her husband of 15 years, the self-proclaimed "bad boy" rapper Bobby Brown; and her best friend Robyn Crawford, who was her confidante before her career exploded at 21.

Houston's first album sold 25 million copies and produced three No.1s. Crawford became her tour manager and possibly her lover, an idea on which Broomfield hangs a great deal. I could not work out if either Crawford or Brown had granted interviews, but they are both strongly represented in old footage.

This is actually two films, melded together. Music film producer Rudi Dolezal shot much of the early footage, including some fabulous material of Houston's 1999 German tour. After several years trying to finish his own film, Dolezal joined forces with Broomfield, who shot new interviews with her friends and fellow musicians.

Broomfield's thesis is that part of the reason Whitney was so unhappy was that she was unable to come out as lesbian; and that once Crawford left the team, the singer crumbled. Having grown up in a gospel-singing New Jersey Baptist church, she was unable to face the condemnation of her family and community.

Her strong-willed mother, Cissy, confirms in an interview with Oprah after her daughter's death that she would have been horrified if she had come out as gay. Broomfield also quotes Brown, who says that despite his many differences with Crawford: "I really feel that if Robyn was accepted into Whitney's life, she would still be alive today."

Who knows? Others in the film say she was bisexual. One of the film's strengths is it can be read in a number of ways. Sexuality might be one part; an early introduction to drugs by her brothers (according to the film) would be another. Broomfield doesn't pretend he knows what happened, but there is a telling comment from the star herself: "Success doesn't change you. Fame does."

The biopic can't be far away.