Whenever the human art installation that is Daphne Guinness walks into a party, the conversation stops. First you notice the hair, a punkish, white-blonde updo edged with sweeping black streaks, then the armor-like silver jewelry covering the length of every finger. But it’s her improbably vertiginous shoes — platformed at the front but heelless — that make you gasp. How on earth does she walk in them? She will tell you they are as comfortable as trainers. They look treacherous, a little sadomasochistic, but rather fabulous too.

So it’s a shock when I arrive at Guinness’s imposing Chelsea town house with its grand sweeping staircase to see her running down the steps in Mary Jane flats and dressed down in loose black thinly pleated Issey Miyake trousers, a cut-out asymmetric top that reveals most of her tiny waist and chest, and a thin black cardigan. She is make-up free and the streaks in her hair are now fuchsia pink. Even her trademark pompadour is softer and gently collapsed.

“Let’s go to the drawing room,” the 56-year-old brewery heiress says as she leads me toward the stairs, past a giant rack hanging with sumptuous couture dresses; endless iterations of her exceptional shoes are lined up underneath. No more room in her closet? “No, no, that was for a shoot.” But they’re your clothes, right, I ask, because they couldn’t be anyone else’s. “Yes, they’re mine.”

We enter a vast room overlooking the grounds of the Royal Hospital, which is quite apposite because she sometimes dresses like a Chelsea Pensioner, minus the trousers. Old paintings in all shapes and sizes cover the dove gray walls (including one of her grandmother Diana Mitford, painted by Diana’s novelist sister Nancy in 1928). A long bar heaving with alcohol (there are no bottles of Guinness because she only drinks it in Ireland) takes up the length of one wall. An open packet of Twiglets sits in a glass.

The tiny beauty sits opposite me on a long, dark-red velvet sofa. She starts speaking in a fast, continuous flow, going down different alleyways, her words tinged with a deep melancholia. Yet the assumption that she is a red carpet Valkyrie (she has appeared on several magazine covers, written articles on fashion, curated a show from her own archive for the Fashion Institute of Technology in New York, designed clothes and jewelry, as well as collaborated on a scent, Daphne, for Comme des Garçons), and therefore supremely confident, couldn’t be more at odds with the self-effacing and timid woman in front of me. Instead of the magnetic, bombastic force you expect, she is sweet and gentle.

We are meeting to discuss her fourth album, Sleep, a beautifully symphonic and contemplative elegy that brings to mind the Pet Shop Boys. Its tracklist includes the songs “Volcano”(“I might look like an icicle but underneath I’m a volcano”) and “Hip Neck Spine” (a sample of her own bones being cracked by a chiropractor features), which echo Sixties chanteuses and Seventies/Eighties pop stars such as Debbie Harry and Grace Jones.

Guinness credits David Bowie with encouraging her to start recording after the pair met at a lunch in New York. “I would not be sitting here if it wasn’t for him,” she says. They became good friends after realizing they had much in common. “We’d discover we were reading the same books and into the same funny musical things.” He introduced her to his producer, Tony Visconti, who worked with her on her first album, as did Bowie. “He got very involved,” she says of the late music legend.

Music has always been in her blood. She remembers hearing her father (Jonathan Guinness, 3rd Baron Moyne, son of Diana Mitford and Bryan Guinness; her mother was the artist Suzanne Lisney) playing the piano in the chapel of the former monastery her family owned in the Spanish mountains (Salvador Dalí was a neighbor and frequent visitor), where she partly grew up. She loved listening to Bach, Beethoven and Chopin as a child. Singing and music became her escape. “It kept me sane forever,” she says. “It saved my life from year zero, but I never thought it would be a career.”

Instead of the magnetic, bombastic force you expect, she is sweet and gentle.

At St Mary’s, Wantage, the Oxfordshire boarding school she was sent to at 11, her talent was recognized and she was made head of music. In her final year she interviewed for the Guildhall School of Music and Drama in London, dreaming of becoming a singer, but her life took an unexpected turn. On a ski trip to St Moritz, Switzerland, she met her future husband, the shipping heir Spyros Niarchos. They were married a year and a half later and she moved full-time to the Swiss alpine resort where his family lived. Aged 21 she gave birth to their first child, Nicolas, now 35 (a contributor at The New Yorker). Two more followed, Lex, 33, and Ines, 29.

The young bride was already part of two great British dynasties (the Guinnesses and the Mitfords) and, by marrying into the Niarchos family, she entered a third gilded prison. Her parents, who she says “never really looked after me” and who she describes as “distant”, had warned her from a young age that her surname and accent would never do her any favors, a sentiment that would color the rest of her life.

“The teachers and the girls at school didn’t really understand or believe me when I told them how I really lived. There was no point telling anybody anything about my home life because you were sent to detention for being a downright liar.” Money, or the spending of it, for example, was frowned upon at home. When she proudly, but unwittingly, announced one day at school that she was related to the Fascist politician Sir Oswald Mosley (he was the second husband of her grandmother Diana), it did not go down well. It was only while watching the announcement of his death on the BBC news in 1980 that she finally understood. “We all have to come from somewhere,” she says sadly. “A lot of my life has been a misunderstanding.”

At the age of five she was brutally attacked and taken hostage by Tony Baekeland, a violent schizophrenic whose mother was a friend of her own, in her parents’ house in Kensington. She was alone at home (except for the housekeeper) on the day of the attack when Baekeland broke into the house and put a knife to her throat, proclaiming death to all women. He dragged her out to the street, the knife still at her bleeding neck. It drew the attention of the housekeeper, who intervened, and he escaped just as her mother returned from lunch.

Baekeland went on to kill his mother the next day, for which he was imprisoned, and then later, following his release, stabbed his grandmother in America, who survived. He himself died by suicide in the New York prison Rikers Island not long afterward. The incident left Guinness understandably traumatized, particularly as the matter was never properly addressed by her parents.

In addition she would discover that her father (whose first marriage to Ingrid Wyndham produced Guinness’s older three half-siblings, Catherine, Jasper and Valentine) had a second family with another woman. Guinness is now close to her younger half-brother, the stylist Tom Guinness, as well as her two other half-siblings, Diana and Aster. You can imagine why, searching for security, she chose to get married and have children at such a young age.

She describes her St Moritz years as “cloistered”. “I was invisible. I knew people in the grocery store, I sang in the woods, I went skiing. I was a lot younger than everyone else. I never felt part of it,” she says. Is she still friends with her ex-husband? “Yes, he’s wonderful, very sweet.” It doesn’t sound like she was a society wife. “Never. I never gave dinner parties. I’ve never been able to give a dinner party — utterly terrifying. I long to have those skills. If I’m having dinner with just one person, I don’t know whether to sit them to my right or left.”

It wasn’t until she moved to her family home in Ireland in 2011 (she and Niarchos divorced amicably in 1999), following her meeting with Bowie, that she started recording. They were not the healthiest years, she admits. She spent her days in a dreamlike, monastic state. “I was working 20 hours a day with black mold around me. My sitting room looked like an explosion, like a madhouse with lyrics all over the walls.” She barely ate and only occasionally ventured out. By the time she had finished the album she was a physical wreck. She was rushed to hospital for emergency surgery in which she had a yard of her intestine removed, following which she got E. coli and then had her gallbladder removed a year later.

Tragedy continued to stalk her during her adult years. Her mother died from cancer in 2005, as did her half-brother Jasper in 2011. Her two best friends, the fashion director Isabella Blow and the designer Alexander McQueen, took their own lives in 2007 and 2010 respectively. A new film about Blow has just been announced, with Guinness appearing as a character. “I don’t know what the script is like, but Emilia Clarke [who plays Guinness] is an incredible actress and Andrea Riseborough is a great choice for Issy. I will help in any way I can.”

Guinness has a vast archive of vintage fashion, which she keeps in storage and much of which is McQueen. Who does she admire today? “John Galliano,” she says decisively. We discuss his barnstorming latest collection for Maison Margiela. “Wasn’t that great? It’s so wonderful to see him re-emerge.” She mentions that she has started making clothes herself too. Can you sew, I ask. “No, but I’m quite good at placing fabric. I realized I was wearing more and more black, so I’ve started working on a theory of color. Colors have gone off recently, don’t you think?”

“I’ve never been able to give a dinner party — utterly terrifying. I long to have those skills. If I’m having dinner with just one person, I don’t know whether to sit them to my right or left.”

Blow, who I worked with at Tatler, introduced me to Guinness and McQueen in the early 2000s. I was lucky enough to spend crazy nights with them, racing across Paris during fashion week or out in London. They were like three pirates, totally in tune with each other, in a way no one else could be, speaking almost in code, a language only they understood. They reminded me of three rare and elegant, but broken, birds.

I’ve often wondered, over the intervening years, how Guinness would cope without them. They were so strong together. But I’ve realized there is something innately resilient and hopeful about her; she has a curiosity for life. “I’ve had to do a lot of looking into my brain,” she says. “I’ve had MRIs. I have anxiety pure and simple, PTSD — it’s an extreme form and very difficult to cure. I’m always floating on very thin ice.”

Female friendships are also something she has struggled with. “I find it hard to keep in with friend groups, I’ve always been a little removed,” she says. She is close to Kate Moss but when I ask her who she considers her best friend she immediately replies, “David LaChapelle”. The American photographer shot two videos to accompany the new album, appearing in one of them. She also mentions RuPaul, whom she met through Bowie at a Fourth of July dinner in LA. The drag queen came up to her and said: “I’ve been trying to get you on my show [RuPaul’s Drag Race].” Two days later she made her first appearance in the series. “He’s become such a good friend, he’s wonderful,” she says. “It’s good to have someone on the outside to bounce ideas off. He’s been in masses of bands, he’s got such a wide knowledge of music.”

What do her children make of her music? “I don’t know, I haven’t asked them. They know what I’m doing. We talk about other things,” she says, adding that she recently had dinner with her son Nicolas at a Polish restaurant in South Kensington.

Love is the one subject she is less forthcoming on. She went out with the actor Tom Hollander in the early 2000s and has famously dated the married French philosopher Bernard-Henri Lévy, who she has described as the love of her life. Has anyone replaced him — indeed, is she still with him? “Who knows,” she says elliptically. Does she call him BHL? “No, Bernard. You know people hated the idea of me being happy with him — people do not like seeing others happy, they do everything to ruin it.” Who those people are she doesn’t elaborate on. “I don’t go out that much,” she continues. “If I ever manage to get out of my front door, maybe I’ll meet someone … hopefully at some stage … I wish I’d spent more time on my relationships. But you can’t have it all.

“If I could do my whole life again I would join the army,” she suddenly says. Really? “I like exercise, target practice. I saw Private Benjamin.” She likes a uniform too, doesn’t she? She has stuck to a very defining look for more than 20 years. “Yes, but I also like the idea of being always around people, like you are in the army.”

As we say goodbye she tells me she’s returning to designing and she’s writing a memoir. “We’ll have to see where I get to … ” she says, drifting off. “I’ve written quite a lot of it, all in longhand. There are some things I’m not sure about saying — maybe they’ll have to go into a vault. It’s been an interesting life.”

Vassi Chamberlain is a Writer at Large at AIR MAIL