FOR all their monumental achievements – five consecutive US number ones, 12 in total, a body of work that made them the most successful girl group of all time, glamorous gowns, worldwide fame – there was a dark side to success that makes it tempting to see the story of The Supremes as, if not quite tragic, then certainly bittersweet.

Not so, says founding member Mary Wilson, the only Supreme to be in every line-up from 1958 to their farewell show at the Theatre Royal on London’s Drury Lane in 1977.

“People might think that, because I get wheeled out so often to talk about the unhappy times, but I have a great life.

“I adore being Mary Wilson of The Supremes,” she says on the phone waiting for a flight from San Francisco.

“I’m a great believer in life being full of ups and downs, so there were moments of unhappiness, but also great joy. There are things I wish I could change, it’s not been perfect.

“We are human beings so of course it isn’t perfect – only Jesus Christ is perfect, so I have been told, and I believe that.

“But I wish I had more wisdom not to sign our name away. I wish I could’ve done more to help my friend Florence.”

Of all the darkness that shadowed The Supremes, the story of Mary’s school friend Florence Ballard is the one true tragedy.

It was Florence who was noticed first. She recruited Mary, who called up her new friend Diane (later Diana) Ross.

Ballard’s gutsy soprano made her the most powerful singer in the group, but her looks were not those required by Motown, and she was ousted from the group in 1967 to be replaced by Cindy Birdsong.

Florence battled alcoholism and chronic depression before dying in near poverty in 1976.

“Life was not very fair to Florence, as it isn’t fair to millions of other people, and that’s why I’m so grateful for the life I’ve had because it has given me a platform to speak out on things and to take on humanitarian work that can maybe help some of those people,” says Mary, who was awarded a Lifetime Achievement Award from the National Foundation of Women Legislators and, in 2003, was appointed as one of nine Culture Connect Ambassadors, taking her to Bangladesh, Pakistan, South Asia and South America. She has also participated in the Trade and Civil Life Conference and spoken to children in Mozambique and Botswana about the dangers of HIV and Aids.

“You know, I’m one of those people who isn’t afraid to be up front, and if there’s a wrong to be righted I will speak out.

“People always ask about a reunion of The Supremes and I will never say never, although I will say it’s not something that’s percolating at the moment!”

There was a reunion in 2000, but Mary’s involvement was scotched because the promoters couldn’t agree a fee – reportedly offering Diana Ross four times as much.

Ross carried on with two Supremes, Lynda Laurence and Scherrie Payne, who had joined years after her departure in 1970. Poor ticket sales saw the tour end after just a handful of dates.

“Diane and I are sisters, and sisters fall out from time to time, though I would say that whenever we have fallen out it has been about business, nothing personal,” says Mary with superbly honed diplomacy.

“We’re not in day to day contact, but if there’s an occasion that requires a card or for one of us to pick up the phone then we do. But it’s not a daily thing, let me tell you.”

A regular on British stages ever since The Supremes played the first Tamla Motown Revue with Smokey Robinson and the Miracles, Stevie Wonder and Martha and the Vandellas in 1965, Mary is looking forward to her theatre tour.

“Of course I’ll do The Supremes hits, but I get to sing a lot of other material as well.

“I’m like a little Tina Turner, you know – I can sing rock, jazz, R&B and pop as well.

“We do some Rolling Stones songs, some Stevie Wonder, it’s a very eclectic show.”

Best of all though, she has a new album which she hopes will be out in time for the tour – and it turns out she has been working with Eddie and Brian Holland, of the hit making Holland-Dozier-Holland team that racked up countless hits, including ten of The Supremes’ 12 number ones.

“Oh yes, I’m so glad about that. Everyone always goes on about the old stuff, which I love, but it’s great to be doing new material as well.

“The album is all original songs, and although at sixty-six-and-a-half-years-old I’m not going to be competing with Lady GaGa, it is a contemporary sound.

“Mind you, whenever I get together with Eddie and Brian we can’t help but start talking about the old days – it always happens!”

• Mary Wilson plays the Pavilion Theatre, Bournemouth on February 27, 2011, with The Chi-Lites, who’ll be performing on their first UK tour since 1984.