They wore long, tubular evening gowns, shimmery with sequins, and they undulated their lissom bodies and waved their elegant arms through a dozen pop-soul hits that brought an instantly recognisable bounce to the soundtrack of the late 1960s. The Supremes weren't just the most successful girl group of the decade, they were in the top five pop-rock-soul acts of any gender or nationality. They broke records as well as made them: for the biggest number of US No 1 hits (12); the largest number of consecutive No 1 hits (five); the first album by a girl group to top the album charts (The Supremes A'Go-Go); and, most significantly, being the first black female music act to appear on television, on The Ed Sullivan Show.
It was in December 1964, and was a landmark in black consciousness. "I've had Oprah Winfrey and Whoopi Goldberg both say to me, personally, that seeing The Supremes on the Sullivan show made them recognise that, hey, maybe I could do that too," says Mary Wilson, co-founder of the original group and the only singer to survive its many incarnations, before it packed up in 1977. "It seems that we inspired people to see what they could become. It wasn't something that was a given, then – to be black and know that you could make it."
A mistress of understatement, Ms Wilson is a big, sassy dame in a short black frock, dark brown hair as sleek as a seal, long silver fingernails and tons of showbiz chutzpah. After 16 years of singing background harmonies behind Diana Ross and, later, Jean Terrell, she gratefully embraced a solo career. Now 64, she still sings in cabaret and jazz clubs around the world, for nine months of the year. She's not, however, in London this week to sing "You Can't Hurry Love" and "I Second That Emotion" and other Supremes classics. She's rather indignant about the prevalence of "a lot of fake, phoney groups" – ie Supremes tribute bands – "working in Europe, until it's got to the stage where agents won't book me, they'll get the cheaper phoney group instead." She's here to open an exhibition at the Victoria & Albert museum called The Story of the Supremes, from the Mary Wilson Collection.
At first sight, it seems to be no more than a display of frocks, presented like precious artworks in that respectful V&A style – fabulously long swishy concoctions of tulle, silk and millions of beads and sequins, weighed down by rhinestone and pearl accessories – but you soon discover that there's a lot more going on. This is a frock show with attitude, with social history and political bite, in which The Supremes aren't just celebrated but given a political context and emblemised as agents of massive change. As TV monitors remind you, their heyday, 1964-1970, coincided with the battle for human rights fought in the riot-torn streets of Detroit, climaxing in the march on Washington and exploding with the assassination of Martin Luther King in 1968. It is the exhibition's provocative thesis that Wilson, Ross and Florence Ballard, the third founder-member, were a vital cultural catalyst. "How socially subversive could three sequinned girl singers possibly be?" asks a billboard in the entrance. The answer is: "Very, apparently."
Many people know the story of how the girls grew up in Detroit's experimental Brewster-Douglass housing projects and met at the junior high. They shared a love of music and were put together as the Primettes, a girly spin-off from a male group, The Primes, whose manager took an interest in the 14-year-olds. When they joined Berry Gordy's Motown label in 1961, and changed their name to The Supremes, they were still kids from the block, who bought dress patterns at the five-and-dime store and ran up frocks on Singer sewing machines. Their first eight singles failed to trouble the charts and they became known as "The No-Hit Supremes". Their transformation from girls-next-door into slinky crooners with Marge Simpson hair and world-conquering moves has been attributed to Gordy, their charismatic and forceful boss (and later Ross's lover). But Wilson says it was the girls' own doing.
"People think we had the look imposed on us. No, we did that. We went to Saks Fifth Avenue and bought what we wanted. We were the kind of girls who always played dress-up. We had an idea of what was class, and we'd take the clothes to Motown and they were wise enough to understand that, yeah, it was a little different from all the others. It was our little ace card."
But Mary, I ask, what did three girls from Detroit's segregated housing sector know about class? "Oh, we knew," says Ms Wilson, smiling at my dimness. "Our parents always got Vogue magazine."
The Motown empire had its own charm school, and supplied the girls with an etiquette coach called Maxine Powell. What was the best lesson she taught them? "How to get in and out of a limousine." She giggles at the memory. "Ms Powell was a little bit broad in the back, and she'd demonstrate how not to get into a limo, and we'd just die laughing because she was so hilarious. We had to learn how to kinda slide in, in case the photographers got you. Her other thing was, How to Sit and be Interviewed on a Stool – whatever happens, always keep your knees together."
The girls even took deportment class with books on their mile-high beehives. "Lots of the Motown acts took the class," she says. "The Temptations, Martha Reeves and the Vandellas. But the Four Tops refused. They were a bit older. They said, 'We already know how to stand up.'"
And so the image of The Supremes gradually came together. They learnt their shimmery stage moves from Cholly Atkins, a professional Broadway dancer and choreographer. Their hair became more and more elaborately styled, "because most of the guys who did it were gay, and to them, the bigger the better. We'd meet people backstage on TV shows and say, 'You wanna work with us?' And they'd show us things, and we'd say, 'We like that.'" It sounds, I say, like three queens with a throng of courtiers. "Princesses, please," says Wilson. "We weren't married then.
"There were many black artists before us," continues Wilson, "pioneers like Sammy Davis Jnr, Chuck Berry, Eartha Kitt. We came after them, but we arrived just when the world was beginning to open up. Countries were starting to open up to what people of other cultures were all about."
Not that everyone was crazy about other cultures. The Daily Mail characteristically reported that three singing "negresses" had come visiting. "It wasn't a word used in the US at the time," says Wilson. "We read it and thought, What? Who are these three black negresses?" She laughs – a rich, Ethel Merman guffaw.
Their success coincided, rather spookily, with the end of the human rights battle. In 1961, John Kennedy had backed King's stand against the segregation laws, and been elected president. The following year, The Supremes hit the road and found themselves singing to segregated audiences (and hearing rocks being flung against the tour bus). In 1963, King rehearsed his "I have a dream" speech in Detroit, before taking it to Washington. Kennedy was assassinated and his successor, Lyndon Johnson, passed the Civil Rights Act, which effectively banned segregation all over the United States. Was it a coincidence that The Supremes had their first No 1 hit shortly afterwards, and began an unbroken run of success? The theory that political harmony meant increased black record sales doesn't wash. The hits kept climbing the charts during the terrible riots that followed the passing of the Voting Rights Act in 1965, giving all US citizens the vote. At a performance in Cleveland, fans had to file past National Guard tanks because of the likelihood of race riots. Detroit itself went up in flames in 1967 near Motown headquarters and 43 people died. King was assassinated the following year (the girls sang "Somewhere" for him on The Tonight Show) and America settled into a new future, where the race issue was eclipsed by Vietnam.
This was the background against which The Supremes sang "You Keep Me Hangin' On", "Love is Here and Now" and, perhaps their best song, "The Happening". How did they stay so perky and upbeat? "It was supposed to be a big hit movie, The Happening, and it was a big deal for us because we were one of the first to do a movie soundtrack. So we were happy. You can hear it in the music: 'Hey! We doin' a soundtrack!'" What were her memories of King? "We were doing a lot of public engagements, so we'd always be in the same running team, you know? Berry Gordy was close to him, so the stars would hang out together. People asked us later: 'were you aware of what was going on?' Of course we were. Politics was about the same thing then. Everyone was part of the movement. Politics was part of our job. We all wanted the same thing." But they never became the voice of black protest, did they? They were never in danger of being confused with Malcolm X. "No," says Wilson. "We became the face of the black movement just by being black and prominent – the face of young black women, achieving something."
While her old adversary, Ross, has become newsworthy for public tantrums, Wilson sails on as the benign face of the old Supremes. She recently nailed her colours to Hillary Clinton's mast. Does she think it more important for America to have its first black president or its first woman president? "They're equally important. I think there's enough of us – I'm speaking as a black, now – to vote Obama in, but I think we need a woman first, because the world needs healing. In America especially, I think we need to heal a lot of ideas that've gone astray. America's a great place of possibility, but right now it's about money, and that's taken away from the real things in life."
So speaks the girl from the segregated housing block who once had lessons on the correct way to enter a limo, and now stands at the V&A Museum, surveying the sequinned evidence of how she and two schoolmates changed the world.
The Story of the Supremes from the Mary Wilson Collection, V&A, London SW7 (020-7942 2000), to 19 October