You could dine out for a lifetime on Bob Mackie’s stories. After 60 years of designing sequin-encrusted stage costumes for Cher, Bette Midler and Diana Ross, to name a few, the 79-year-old has anecdotes to spare. He sprinkles them into conversation like glitter.

He once dressed Elton John as Donald Duck, complete with tail and webbed feet, making it very difficult for the Rocket Man to play the piano. He worked with Tina Turner during her post-Ike transformation, when “she wanted to look like a sexy cave woman”. Barbra Streisand, he says, “was always questioning everything. ‘Does this really look good? Can we try on three or four, then decide?’ With that kind of sensibility, you work harder, believe me.”

He was friends with Marlene Dietrich, an uber-perfectionist whose gowns would be worn out by multiple minute alterations before they had even left the fitting room. She would also root around “in our community refrigerator, and throw out old food if she found it. And if someone was sick, there was always something in her purse that would work. She was like a grandmother.”

Bob Mackie, who sprinkles anecdotes like glitter. Photograph: Linda Nylind/The Guardian

And then there is Cher, his closest collaborator, with whom, in the 70s, he developed a design philosophy best described as “more razzle-dazzle, less fabric”. Without him, Cher has said: “I would have been a peacock without feathers.”

It is in the shadow of Cher – or, at least, of two Cher-like mannequins – that we meet in a hotel in London. Mackie is in town for the launch of a vast wardrobe clearance. Two days hence, he will board a cruise ship from Southampton to New York City with more than 100 of his sketches and gowns, for a seaborne exhibition to promote a sale at Julien’s Auctions, in Los Angeles and online, on 17 November.

Cher in a Bob Mackie creation in 1978 in Los Angeles. Photograph: Harry Langdon/Getty Images

Why sell the frocks now? “When you have been in a business as long as I have,” he says, “you end up with a lot of interesting things. I certainly don’t need to keep the lot of them. I still have a lot of memories left.”

Although he jokes about his age, Mackie comes across at least 20 years younger than he is: he poses energetically for our photographer, goofing around between the two immobile Cher surrogates. One models a yellow halterneck jumpsuit decorated with a huge sequinned sunflower, the other a crimson, cheongsam-inspired gown embroidered with a gold dragon. Mackie is neatly dressed in a gold-buttoned navy blazer with a cobalt-blue, silk pocket handkerchief. His hair is the colour of weak tea and he has a wide, boyish face. He looks like the treasurer of a local Rotary Club, or a daytime gameshow host, rather than a purveyor of showgirl chic. His face clouds over briefly, just once, when he runs a finger along the seam of the yellow jumpsuit and says it needs to be tweaked. (“I knew he wouldn’t be happy with that,” mutters one of his colleagues.)

Some of Mackie’s most vivid memories are of Cher. When they met, he says, her look was totally new: “She was the first hippy, really; the bellbottoms, the fur vests, the long straight hair. She created a whole fashion turnaround.” Together, they built her next visual incarnation, which often centred on her naked abs. “The doctor,” he says, “said she had some kind of strange malady of tight stomach muscles.” (Mackie refers frequently to the lithe proportions of his most famous canvas; he has been known to point out that her armpits were the best in the business.)

Mackie at the 1974 Met Gala, with Cher in the feathered ‘nude’ dress he created for her. Photograph: Ron Galella/WireImage

Their fashion hits included the sequin-studded, feathered “nude” dress she wore to the 1974 Met Gala, which created “a lot of hullaballoo”. Afterwards, “I got a lot of calls from performers wanting something ‘like Cher wears’ because it got a lot of attention.”

More eyeballs were drawn by Cher’s 1986 Oscars ensemble, a sort of “Big Bird goes for a night out with Maleficent in Las Vegas” number, with a perilously low-rise skirt. The outfit was conceived as a dig at the Academy, which, Cher felt, had snubbed her that year. “I wasn’t sure if it was the proper, polite thing to do,” says Mackie, noting that he was “apprehensive” about it (he is always apprehensive, he explains; a wardrobe malfunction is often just a millimetre of tit tape away). “Some people were horrified but it was in every newspaper,” he says. Cher loved it, of course. He says, with a knowing smile: “Halloween’s her favourite holiday.”

It was often Cher pushing Mackie to create more revealing and outlandish outfits, not the other way around. For example, she came up with the mesh bodysuit worn to mount a cannon in the video for If I Could Turn Back Time. He thought it was “vulgar and horrid. I told her: please, I don’t want any credit for this.”

Elton John dressed as a duck. Photograph: Chris Morris/Rex/Shutterstock

Mackie grew up in a more reserved time. His childhood sounds pretty dour: between the ages of six and 14 he lived with his British grandmother, who “believed children should be seen and not heard”. His escape was the cinema. He recalls the “religious experience” of seeing the ballet scene from An American in Paris for the first time. He built mini movie sets, complete with stars dressed in paper outfits, on top of his dresser.

In 1960, he married LuLu Porter, a singer, actor and acting teacher. They had a son, Robin, and divorced after three years. That year, when he was 23, he started working on The Judy Garland Show, assisting costume designer Ray Aghayan, who became his partner, in life and business, until his death in 2011.

Garland was, he says, “a phenomenally talented individual, but she had been so mistreated in the beginning, as a child, that she was very troubled”. The show was disastrous, with a high turnover of personnel, but the situation proved unexpectedly useful for Mackie, as he quickly met almost everyone who was anyone in the industry. It sounds tougher for Aghayan who, in the past, Mackie has said, received phone calls from Garland in the middle of the night, asking him to take her to hospital. Clearly, the dark side of Hollywood is never hidden for long, no matter how thick the crust of glitter.

Cher backstage at the Academy Awards in 1986. Photograph: Bettmann Archive

Mackie is also from a time before debates about cultural appropriation in design were commonplace. Cher herself has recently been criticised for the 1973 song Half-Breed – even that title might make a contemporary audience wince – and for the Mackie-designed Native American war bonnets she wore when singing it.

Mackie doesn’t understand the fuss. “People are becoming much too sensitive about their cultures; we’re losing the humour, and that is very sad. She wore that for 40-odd years. Now, all of a sudden, you have a couple of hard-nosed people saying: ‘Oh no, she can’t.’ Well, you’re a little late honey.”

That said, he confirms that Cher won’t be wearing a war bonnet for her forthcoming tour, even though he has faithfully remade a lot of the other costumes. “I just ended up doing a whole new costume, with a different twist to it.” (The claim that Cher can sing this song because her mother has some Cherokee heritage seems to hold less water these days. Mackie says: “I don’t know how much Native American blood Cher has in her, I don’t think very much. I think she gets her dark good looks from her Armenian father.”)

Mackie’s life is still monopolised by work; he is working on the costumes for a huge Cher-themed Broadway musical. “I think I’m the oldest living designer in Hollywood,” he says. Will he ever retire? “I hope not.”

Work has been a balm in difficult times. The year 1993 was unbearable. His son died, at 33, from an Aids-related illness, and Mackie was forced to close the New York fashion business he had launched in order to move beyond pure costume design. Rather than lying low to grieve, he went straight back to work, with Midler, on the TV movie Gypsy, a project that, he has said, saved him.

Midler, of course, is yet another gay icon: Mackie’s life seems to be inextricably linked with women with that epithet. He himself has been called, “the patron saint of drag queens,” he says. He talks fondly about being chased down the street by half a dozen drag Chers. Gay culture has changed a lot, he says. “It used to be something you didn’t discuss; now everyone knows everything and everyone’s an expert.”

Bette Midler in the TV movie Gypsy. Mackie says working with her on this project saved him at a difficult time in his life. Photograph: Kobal/Rex/Shutterstock

Has Mackie created gay icons – by swathing them in sequins – or have existing gay icons approached him because they like his aesthetic? “It works both ways,” he says. “Certainly, most gay icons like to dress up.” They are also, often, women who pile on the shimmer to shine at dark times, who must always project otherworldly charisma and talent. That is quite a challenge, says Mackie, “because your public always expects to see it. They want to be delighted – ‘Oh, she’s so beautiful did you see what she wore?’ – but very often these actresses are just homebodies with kids at home and a husband. It’s when they go out and make the bucks they have to change the whole thing.”

Perhaps the biggest surprise about Mackie is his earnestness. “I’m very serious about this,” he says. “It’s not just flamboyant, crazy stuff. It’s all very worked out.”