LONDON - As heartbroken friends and fans mourned George Michael online and at his homes across Britain, questions swirled about the health and final weeks of the electrifying pop singer before his death on Christmas Day at the age of 53.

Once an indisputable sex symbol of the peak-MTV era, Michael appeared overweight and nearly unrecognisable in photographs, reportedly from September, according to website TMZ on Monday (Dec 26).

News media attention also fell on a 2015 tabloid interview with a relative claiming the star was abusing drugs and putting his life at risk.

And after years of arrests related to drug use, as well as confessional interviews and health scares, he had largely retreated from the public eye, while his creative output had all but ceased.

Paul Gambaccini, a radio and television presenter who had known Michael since youth and represented him during a 2011 tour, said in an interview that he was not surprised by the singer's death because Michael was "not completely well" and had a "close brush with death" five years ago when he nearly succumbed to a bout of pneumonia. Doctors had to perform a tracheotomy.

Police officials, who had announced Michael died in "unexplained but not suspicious" circumstances at his home in Goring-on-Thames, England, could not be reached for further details on Monday because of Boxing Day.

The singer's manager Michael Lippman on Monday declined to elaborate on his statement that Michael had died of heart failure, "in bed, lying peacefully". Forensic experts said an autopsy report could be ready in a couple of days.

While admirers sought to focus on Michael's previously unreported donations and philanthropy, and neighbours remembered his charm as a low-key celebrity in their midst, a more complicated image of Michael's life in recent years loomed, as well.

Several friends and associates, while declining to discuss details of his health, noted that Michael had a long history of hard living. In 2007, he was sentenced to community service and barred from driving for two years after he had been found asleep at the wheel and under the influence of drugs. The next year, he was arrested in London on suspicion of possessing crack cocaine.

"I've done different things at different times that I shouldn't have done, once or twice, you know," Michael said in a 2009 interview with The Guardian, in which he discussed his ups and downs with sex, sleeping pills, marijuana and crack. "People want to see me as tragic," he said. "I don't even see them as weaknesses anymore. It's just who I am."

In the summer of 2015, he and his publicists denied that he was facing serious drug addiction after a report published in a British tabloid, The Sun, quoted the wife of a relative saying: "I'm petrified he will die."

Michael responded on Twitter: "To my lovelies, do not believe this rubbish in the papers today by someone I don't know anymore and haven't seen for nearly 18 years." He added: "I am perfectly fine."

Rather than dwell on his difficulties, some close friends on Monday highlighted another dimension of the man they knew, describing him as a generous benefactor given to quiet and spontaneous acts of kindness.

"He was a closet philanthropist," said Gambaccini, recalling how in 1994 the British government cut aid to the Terrence Higgins Trust, an Aids charity. To make up for the shortfall, Gambaccini, a patron of the trust, said he had sought to raise £300,000. But in the end, he did not have to try too hard, as Michael donated most of the money.

"He never wanted public recognition," Gambaccini said.

TV presenter Richard Osman wrote on Twitter on Monday that Michael had secretly contacted a woman who appeared on Deal Or No Deal, a British game show, to give her £15,000 (S$26,664) needed for an in vitro fertilisation treatment.

Sali Hughes, an author, wrote on Twitter that Michael had once tipped a waitress £5,000 "because she was a student nurse in debt".

And Emilyne Mondo, a volunteer at a shelter for homeless people, posted that Michael had worked there anonymously.

"I've never told anyone," she said. "He asked we didn't. That's who he was."

For some neighbours of Michael, his turn away from the spotlight and towards personal privacy made him just another member of the community.

Amanda Holland, 56, a neighbor of Michael in Goring-on-Thames, in Oxfordshire, and an amateur actor, once invited him to a play in which she was performing. "He's an international superstar - I thought, 'There's no way he would come to a local thing,'" she recalled.

"But he did, and he was fabulous, and he was kind and he was generous."

Michael's final tour Symphonica ended in the fall of 2012, and a live album drawn from those performances, released in 2014, represented his most recent commercial output.

There was some potential movement in his career of late. This year, Michael received a bump in pop-culture relevance when the film Keanu, a comedy from Keegan-Michael Key and Jordan Peele, featured his music prominently in its plot - and not as the butt of a joke, as Michael had come to be treated by some, especially after being arrested on charges of lewd conduct in a men's room in Beverly Hills in 1998.

The film-makers assured Michael's manager Lippman that they would use his music respectfully.

"A golden opportunity dropped in our laps," Lippman told Billboard, and then went on to tease the re-release of Michael's 1990 solo album, Listen Without Prejudice Vol. 1, which had been expected this fall. "We were trying to find as much exposure as possible." (That re-issue was subsequently pushed back to March 2017, to coincide with a documentary, Freedom, about Michael's life.)

Producer Naughty Boy, who has worked with Beyoncé and Sam Smith, told the BBC this month that new music from Michael was a possibility. "He's got an album coming out next year, and he's going to be doing something for my album as well," Naughty Boy said. "I don't know what to expect. And, to be honest, he's more mysterious than anyone else, so I'm actually excited."