Annabelle Neilson has died aged 49.
The socialite - who was best friends with Kate Moss, and the late British fashion designer Alexander McQueen, who died in 2010 aged 40 - has passed away, police have confirmed.
Police told DailyMail.com that her death is not being treated as suspicious and that an ambulance was called to her home in Chelsea, West London, on Thursday (12.07.18).
Annabelle was left devastated when Alexander died, and claimed she regretted not accepting his marriage proposal.
Speaking about the designer, who she called Lee - his real first name - Annabelle said: "He was my brother, my boyfriend, my soulmate. Most of the time people called me Mrs McQueen.
"Quite often we were sharing a bed.
"The truth is I was happier with Lee than with anyone else.
"He asked me to marry him towards the end and I said no. I wish now that I had said yes."
Annabelle married millionaire banker Nat Rothschild after eloping to Las Vegas in 1994, but the pair went their separate ways in 1997.
Earlier in the decade, the 'Ladies of London' star met Kate while working for Alexander, and she later described the model as her "best mate".
She said: "Kate is my best mate and I love her like a sister. Yes, she's an icon but to me she's just Kate.
"We fight over stupid things, then we kiss and make up. We share clothes, we share everything and her fame has never been an issue.
"She always looks out for me and I look out for her. We've got each other's backs. I'm very proud of her and she's very proud of me."
Annabelle was a heroin addict aged 16 but managed to quit hard drugs, and late credited the Class A substance with saving her life.
She said: "In a way, heroin saved me because otherwise I would have killed myself."
The model - who appeared on US model reality series 'Ladies of London' from 2014 to 2015 - posted a picture of herself on Instagram sunbathing in Spain just last month.
She wrote in the caption: "In Spain catching some rays #sun (sic)"