Sandie Shaw is giving me a guided tour of her feet. "That's been taken off." She rubs her finger along the side of her shapely right foot just below a purple-nailed big toe. "Bunions?" I say, nervously, for these are celebrated size seven-and-a-halfs. As she was clocking up three number ones in the mid 1960s ("Always Something There to Remind Me", "Long Live Love" and "Puppet on a String"), Shaw was labelled "the barefoot pop princess" on account of her habit of singing on stage without shoes and it quickly became her trademark. "That one's been shortened," she continues, ignoring my question and stroking her second toe. "And the tendon's been cut so they go straight." She is now pointing at all her toes.
We sit back, side by side, on a sofa in a Soho clubhouse, gazing at her feet, which are propped up on a coffee table at the end of her long, elegant, tanned legs. There is about us something of the reverence we might accord a work of art. "I've had all of it," she muses of her decision, in 2007, to submit her best-known features to the surgeon's knife. "I forgot the face and just did the feet and it was worth every penny. Now I can walk properly, dance properly, and wear the most amazing footwear. I just love wearing shoes." Then she breaks the mood by letting out a great big guffaw of laughter, the sort you might associate with a hen night in full swing.
"If you look in my bag over there" – Shaw points to a jumble of cases next to the photographer's equipment – "I've only brought two frocks for today, but a huge bag of shoes." She places lots of ' emphasis on the "huge". Her accent is uncannily like her contemporary Janet Street-Porter's.
So you didn't wear shoes before because it hurt your feet, I wonder aloud? "Yeah," she replies. I am just about to point out that this is not what it says of her barefoot years in her 1991 autobiography entitled (inevitably) The World at My Feet, when she suddenly corrects herself. "Well, a little bit."
It is an exchange that neatly sums up the 63-year-old Shaw's ambiguous attitude to her own celebrity. There is a part of her that is still playing along with being a 1960s icon, the girl from Dagenham who, along with Cilla and Lulu, was part of a new wave of British girl singers who took the charts by storm. So, for instance, when we get round to talking about her grandchildren – she has four – she describes herself as a "diva grandma". Do you still see yourself as a diva? "No, no," she starts, "not really, but because I've lived so much that way, I tend to behave like a diva."
And indeed she does – in the nicest possible way. There's a stagey-ness about Shaw, both in her dress (her hair may be shorter than in her heyday, but she looks great and is delighted that she seems to have dropped a dress size without even trying) and in her innate sense that she is the centre of attention and therefore must keep everyone in the room – photographer, PR person, manager, (third) husband, make-up artist, me – happy and entertained. It can make her absurdly flattering. "Your face is very familiar," she tells me as I walk in. "I'm sure I know you." We've never met, but what better greeting. It can also, though, make her brassy. When she perches on the arm of the sofa to have her picture taken and her short skirt rides up, she hollers over to me, "No looking you!" then follows this, as an opening gambit for the interview, by asking me, "Are you posh?", which is either plain silly, or just reveals how nervous she is feeling.
On balance, it is definitely nerves because, after her chart success in the 1960s began to taper off, Shaw largely turned her back on music, the spotlight and everything that goes with it – including interviews. "I'm a bit rusty at all this," she explains at one stage, as if apologising for missing a note when giving a rendition of "Monsieur Dupont", her other still-familiar single. Lulu and Cilla may have soldiered on in the public eye through highs, lows and makeovers, but Shaw has for long periods disappeared, principally to train and practise as a psychotherapist, working with people in the arts.
But she never quite closed the door completely on her past and there have been brief renaissances. In the 1980s, the Smiths rekindled her pop career – Morrissey declaring himself an "incurable Sandie Shaw fan" – when she recorded their "Hand in Glove" and they appeared as her backing band on Top of the Pops with their shoes off. Later, though, when on their 1988 album, Viva Hate, the Smiths sang apropos of a fading celebrity, "Did that swift eclipse torture you?", some wondered out loud whether it was a reference to Shaw.
"Well, I don't sit there contemplating my life," she replies when I ask about her attitude to her past. Fame certainly came to her quickly, and young. One day she was a 17-year-old just-out-of-grammar-school girl doing a bit of part-time modelling, the next she had been spotted by Adam Faith, recorded one of his songs, and become one of the faces of the Swinging Sixties. She married another of its names, the clothes designer Jeff Banks, had her own fashion label and her own television series, The Sandie Shaw Supplement.
By the 1970s, though, it had all gone wrong. She began positively enough by taking time out to be a mother, but then her marriage ended, there were well-publicised financial troubles (one cutting mentions her having to work as a waitress), and her attempts to make her mark as an actress (she played Ophelia in Hamlet and Joan of Arc in St Joan) petered out along with her recording career.
"I spent my thirties recovering," she recalls, "and then my forties beginning to enjoy life. When I worked with the Smiths, they really expected me just to run with the ball, but I wasn't ready. I couldn't do it. I was still in shock and traumatised from what had happened before." Anything in particular? "The whole experience. I didn't have any of the protective things that are in place now. I can't really explain what it was. I'm not going through my history again. I had some bad times."
The result was that she decided in the early 1990s to train as a psychotherapist. "I had seen people do terrible things and I was always asking why people behave like this. And then I found out." Why? "Oh, complex reasons. It is humanity. It is how we are. We don't realise that life is fantastic."
Shaw is, she says, finally in a happy place, and it is from this happy place that she has agreed to give her first concert in more than 25 years, at next weekend's inaugural Vintage at Goodwood, set up to celebrate 50 years of British creativity, covering music, art, design, film and fashion from the 1940s to the 1980s. What persuaded her was an approach from Goodwood's owner, Charles Henry Gordon-Lennox, Earl of March and Kinrara, whose sister, like Shaw, is a Buddhist. "Charles emailed me and said, 'I've got this idea.' I'd already had an email from Wayne [Hemingway, the fashion designer, who is co-organising the festival] and ignored it. I'm always getting emails asking me to do things. But because of the personal connection with Charles, I took it seriously. I thought it might be an opportunity to get Charles into Buddhism too." That laugh again. "So I said yes-ish."
Yes-ish is a favourite word of Shaw's – her way, it seems, of reconciling her past with her present. "I don't do anything unless I feel perfectly comfortable with it, and that's why it is always yes-ish. And then it either becomes yes, or, if it feels awkward, no." Stepping back into the limelight after a quarter of a century would daunt most of us. Does she have stage fright? "I don't get nervous about anything now," she replies casually, "and I am part of a show and a concept, and so it makes it easy to step into it."
Her tone is almost too casual, as if she is willing it to be true. Did she ever get stage fright? She laughs, then pauses for a long time and looks straight at me as if weighing up which way to leap. I try to help her out. Do you like performing, I ask, thinking it is a more straightforward question on the basis of what I have witnessed already. "Uuum. Not really, no. I don't enjoy it. I never enjoyed it because I got so nervous, and it got worse and worse and worse, so I stopped altogether."
So why say yes to Goodwood? "Well, I wasn't meant to perform. The idea was that they wanted me to curate a stage. When Wayne came over to see me, I came up with some ideas, then he got more and more excited about my ideas. You see, other women singers were going to perform them, but then I realised I could wear some fantastic frocks." Cue the laughter. "Because I've got to introduce everybody, I'll be able to wear the diva frocks I really want to wear. You don't get to wear them when you're a therapist." Indeed. It might shift the focus from client to clinician.
Shaw's idea for Goodwood is simple but promising. It is all about women performing songs that are usually only tackled by men. She has assembled a line-up that spans the generations and includes Linda Lewis, Sophie Ellis-Bextor and Tahita Bulmer from New Young Pony Club. "I emailed them. I am so shy, I couldn't phone, but everyone I contacted said yes, what a brilliant idea."
The inspiration for the set goes back a long long way with Shaw. "Right from the start, I used to hijack songs that Chris Andrews, my songwriter, had done for Adam Faith, and say it could be brilliant for a girl to do. Songs such as 'I'll Stop at Nothing'. At the end of the 1960s, I did an album called Reviewing the Situation with songs that no one would ever think I'd pick. I turned them on their head – Led Zeppelin, Bob Dylan. I did 'Lay Lady Lay' and I didn't bother changing the lyrics because I thought, how lovely. It reminded me of a Rubens picture and admiring her beauty. Why not? Women do it all the time..."
The album was not a commercial success, but her Vintage at Goodwood set will give Shaw a chance to revisit the whole question of challenging gender stereotyping in pop music. "What has happened since I did Reviewing the Situation is that women have gradually emerged, so that now often the only people doing anything different are girls. We've become the new Elvises. It's about making you think, like taking a song and putting a skirt on it, whereas in the 1960s we used to take songs and take the trousers too. That's how much women in music have moved on."
She's not revealing what songs she and her co-performers will be featuring. As a taster, though, she quotes Bob Marley's "No Woman No Cry": "With a woman singing it to not just one woman but to all women, that becomes a massive song, even more massive than it already is." Any others? "The Smiths' 'Some Girls are Bigger Than Others'. We are talking about calling it 'Some Boys are Bigger Than Others'. That would be much more fun."
Fun crops up a lot as Shaw talks. She describes, for example, what she is doing at Goodwood as having fun. "I'm very much into this concept of play, because music has become so commercialised. It is all about selling a product. No one has any space to play with each other, to be inspired by each other, to be creative. To have a chance to do this at Goodwood is what has attracted such brilliant people to work on it."
Might it lead to a CD? "It will flow its natural course," she replies cautiously. "Its an -ish." That word again, but even with the implicit qualification it marks a change from an interview she gave a couple of years back where she categorically ruled out a comeback, labelling them "narcissistic pursuits".
Music seems to be exciting Shaw right now, but a career in music is another matter. "There was no industry in the 1960s, but it is just how it is now. It is what happens when you corporatise things. I am on the board of the Featured Artists Coalition [which fights for artists' rights over their output] and am so active in it because I believe in artists leading, not being exploited.'
Does she feel, then, that she was exploited as an artist? "Well, that's their job. I wish I was more exploited by EMI." Not quite the remark you would expect from someone who has put all that behind them. "The idea is to be exploited. You want everyone to listen to your songs, don't you? But you don't want to be exploited in a bad way." She stops for a moment. "I'm ranting, aren't I?"
Shaw is currently not seeing clients at the practice she founded, the Arts Clinic, in order to focus on her music, but she continues in a management role where she is known by her married name, Sandie Powell (her second husband was Nik Powell, co-founder of Virgin Group with Richard Branson, and she has subsequently married Tony Bedford).
Has re-immersing herself in music caused her to have any regrets at the way things turned out for her as a recording artist? "You can't recreate the past," she replies emphatically. "You can make something new from now. Otherwise it is sad. And exciting things are happening to me every day." But there are, she concedes, moments when she wishes she had known the things she now knows when she was younger. "I could have done a lot more in my career if I had been as together as I am now." Such as? "I just would have had the wherewithal to do things and to see them through, not get frightened, not be intimidated by people. All the things that lots of people, lots of women, at that time would have gone through."
She seems to be suggesting that those women artists who emerged in the 1960s suffered more than their male counterparts, but when I seek to clarify it, she immediately retreats as if anxious to keep everything bright and breezy. "I've no idea because I'm not a man. I only have a woman's experience. I can only live inside being a woman. I love men and I love what men do. And I love women and what women do. And I love what men and women do together" – biggest laugh yet – "and whatever else in between is fine by me."
So which way now in a career that has been anything but straightforward? Forward as Sandie Shaw, if the set she has put together at Goodwood causes an upturn in demand for her diva side? She's already been back in the studio recording a Billy Bragg track as the title song for the new Stephen (The Crying Game) Woolley film, Made in Dagenham, out in October. Or forward as Sandie Powell, an esteemed therapist in plain black suits whose clients have no idea about her past?
"I'm 63," she protests, "give me a break. I was meant to be retired three years ago. I don't need a career. I don't need to be famous. And I don't need the money." She says it with conviction. "I'm not one of those people," she reassures me, "who are desperate to hang on to it."
Sandie Shaw will appear at Vintage at Goodwood Festival, which runs from 13-15 August (vintageatgoodwood.com)