Her career spans 55 years and, as of next week, 11 prime ministerships. She only drinks champagne and lives like secluded royalty in Monte Carlo. And when she steps out on to Glastonbury's main stage on Sunday, Shirley Veronica Bassey, formerly of Tiger Bay, Cardiff, will show yet another generation that there is nothing like this particular dame.
I am meeting the very embodiment of undimmed, old-fashioned, up-by-the-bootstraps showbusiness sparkle at a west London studio. I adhere to the advice that I should address her at all times as Dame Shirley, but she is delightfully approachable company as we listen to her new album, due to be released the day after she shares the bill on Michael Eavis's farm with the Who, the Kaiser Chiefs and the Manic Street Preachers. Glastonbury may never have had quite such an ab-fab moment.
Bassey has had numerous opportunities to fade away. In 1977, with two dozen hit albums and 12 UK top-10 singles already to her name, she was a winner at the first ever Brit awards, long before they had been given the name, as the best British female artist of the previous 25 years. She first announced she was going into semi-retirement in the early 1980s, to concentrate on charity work.
But Bassey went on to define the art of reinvention, via collaborations with groups such as Yello (The Rhythm Devine, 1987) and the Propellerheads (History Repeating, 10 years later). She became a dame in 1999, sang in the Queen's back garden at the Golden Jubilee concert of 2002, filmed two An Audience With ... shows for ITV, and then toured Britain again last year. "I've been on this wave ever since I was discovered," she says now, and then switches to mock anxiety: "I can't get off! Help!"
Early last month, when The Living Tree entered the top 40, Bassey extended her run of hits to 50 years. The new song was the result of a collaboration with Nikki Lamborn and Catherine Feeney - writer-producers who she says have "breathed new life into me" - and has led to an album, and to Bassey signing to the duo's own independent label. Get the Party Started contains many remixes of her calling-card songs and perhaps the longevity of Bassey's career is not so much about reinvention as about her ability to make an impression on each new generation. At 70, she seems bemused and delighted by her continued success.
"I know nothing about music," she says. "I cannot read a note, I cannot play an instrument, but I know music in my head, and I was born with these vocal chords I didn't even know I had."
As the youngest of seven children growing up in working-class Cardiff, with a mother from Yorkshire and a Nigerian father, she says she received little encouragement to sing. "Someone tried to tell my mother about my singing when I was young, and she said, 'She gets on our nerves sometimes,'" says Bassey. "So that didn't inspire me to become a singer at all. I would sing instead of crying, I remember, and my sister would say, 'Mum, Shirley's at it again. Tell her to stop, we're trying to sleep.' So I was not appreciated, I really was not. But the voice was always strong.
"It was like I was meant to do it because even when I had my first job in a factory, and I was wrapping up enamel ware for export, I'd just sing, and people would stop working. The supervisor would say, 'Bassey, what do you think you're doing? All of you, get back to work.' The whole factory would stop. I didn't realise what I was doing."
There was no easy route to stardom for Bassey. "My manager always said to me, 'You'll only ever be a cabaret singer, you'll never appeal to a family audience.' Boy, did I ever prove him wrong. I started to go into musicals, then variety, then concerts, then pop songs, so I covered all those bases. Variety teaches you so much, because you get so many different artists in one show. I used to stand in the wings and I think I learned something from everybody. The balancing acts, the comedians, the adagio dancers, the magicians.
"These days, if kids do get discovered it's sad, it's not lasting, because they are not taken care of. I was taken care of. They are instant stars, they can't handle it and the inevitable happens - they turn to drugs and drink. My audience grew up with me and introduced me to their children, and their children. So in the end I have a family audience.
"In the early days, with Kiss Me Honey Honey Kiss Me and As I Love You, I was touring England, Scotland, Ireland and Wales for 18 months before they went into the hit parade. They went into the act, and all these people came to the concerts, then the disc jockeys started playing them, and they were [number] 1 and 2. That's how we did it in those days."
Did being on stage terrify her? Not at first. "It was thrilling, I really loved every moment of being on stage, I didn't have any nerves. Nerves come later ... it's weird. I suppose when you start, you have nothing to lose. Then, of course, when you become successful, you think, I could lose all this. I get more nervous now than I ever did."
Yet the joy of communicating with an audience, of subtly stage-managing their emotional highs and lows, remains the same as ever. "I get a great kick out of that. You have to have a beginning, middle and an end, then the other songs fall in between. I find that so exciting, to put an act together, to find songs. You lift them but you can't keep doing that, or you break them. The next song, you must bring them down gently."
On Sunday, at the biggest outdoor music and performing arts festival in the world, she will make that connection with what may be the youngest audience she has ever performed for. "Just when I think nothing exciting's going to come along, this song The Living Tree comes along and then Glastonbury - and you can't say no. I can't, anyway, because this is my destiny. I have no say in it".
· Get The Party Started is released on Lock Stock and Barrel Records on Monday.
