Anastacia: Arnold Schwarzenegger made me sing Whatta Man 12 times

"When they first see me, they just think I'm four eyes and blonde hair," said Anastacia, introducing herself on MTV's reality show The Cut in 1998.

"When I sing, it's very different."

She wasn't kidding.

Her TV debut opened with a long wide shot. Audiences heard her before they saw her. That voice is all purr and growl, like a lion clawing its way through velvet.

As the camera zoomed in, Anastacia strutted down the staircase, her hair in pigtails under a candy striped bucket hat, her midriff exposed by a crop top, in accordance with 1990s pop regulations.

By the time she finished her song, Not That Kind, the phone lines were red hot. Even Michael Jackson placed a call, trying to sign her to his record label.

"It was like a clamouring," recalls the Chicago-born star. "Everyone wanted to sign me."

Pre-fame, reception work was her bread and butter – most memorably at a hair salon that provided a "first glimpse of what it's like to have a glam squad".

But she was always singing. By her early 20s, Anastacia was in demand at Hollywood functions and parties, including Steven Spielberg's wedding to Kate Capshaw.

"I sang a Celine Dion song – I can't remember which one. Then fast forward a couple of years later, and I'm having dinner in this restaurant in Malibu, and it happens that Spielberg and his wife are there having dinner with Tom Cruise and Penelope Cruz.

"I went over and I said, 'You won't remember this but I sang at your wedding, and what's wild is that my dream came true and I'm actually a singer now.

"And Spielberg said, 'The wildest thing is that I'm still married to her', which was hilarious."

Other celebrity encounters were more… er, quirky.

"I played Arnold Schwarzenegger's birthday, and he had me do En Vogue's Whatta Man," she recalls.

"Great song, but he just wanted me to sing it over and over again. I think I sang it 12 times.

"Every time, I was like, 'Oh my God, he wants it again'. It really made me laugh."

After all those years of effort - and infinite encores of Whatta Man - Anastacia finally got to make her debut album at the turn of the millennium.

She was 32. Press releases said she was 27. But if the youth-obsessed pop industry thought age would be a barrier, they were wrong.

Debut single I'm Outta Love was a Top 10 hit in 19 countries, going platinum in the UK, and becoming Australia's best-selling single of 2000.

Anastacia's album, named Not That Kind for the song she performed on The Cut, sold more than four million copies worldwide. This year, the star is touring to celebrate its silver anniversary.

"I pray the songs still sound fresh," she says. "I do feel that they still bring joy for people that have known the songs – whether they were getting over a relationship or whether it was just their party song."

With more than 70 dates across the year, including a triumphant performance at Radio 2's Party In The Park this weekend, she's noticed a shift in her audience.

"When I started, a lot of older people loved my voice because it has the nuances of Aretha Franklin and Tina Turner.

"Now that it's 25 years, I'm getting the younger audience that were in single digits [the first time around] . This is their first time ever seeing me in concert and you can feel their excitement."

The tour is particularly fulfilling for the singer because, at the start of her career, she was prevented from playing live.

"It was an internal situation," she says. "In those days it was vitally important to get played on radio and because of an issue that my record company had with the two major radio stations in America at that point, I was blacklisted."

To this day, Anastacia has never troubled the US Billboard charts. At the start of her career, when she was signed to a US label, that made it impossible to bankroll a European tour.

She had to wait 'til her third album (2004's Anastacia) to show fans what she was made of. Years of pent-up demand resulted in an 80-date trek around the continent, including dates at Wembley Arena and outdoor shows in Italy, France and Ireland.

It was pointedly titled the "Live At Last" tour.

Although it stung not to be successful in her home country, these days she "can't even imagine putting America into my life."

"I'm already working enough," she laughs. "I'm exhausted."

She can trace the change of heart back to 2003, when she performed at 46664, an Aids benefit concert organised in South Africa by Nelson Mandela.

"I was backstage and Beyoncé and Bono were talking to me, saying, 'God, I would love to have a country where I could walk around and people would think I was just a regular person'," she recalls.

"I was like, 'I never thought about it that way'. And in hindsight, I'm very grateful."

That glass-half-full optimism has been a hallmark of Anastacia's career. It kept her going through the years where she was considered un-signable; and was the foundation of her comeback after surviving breast cancer, twice.

As fate would have it, the 25th anniversary of Not That Kind has coincided with a resurgence of Anastacia's music on social media.

"I used to think I'm Outta Love would always be my biggest song and, lo and behold, Left Outside Alone has surpassed that.

"And interestingly enough, Paid My Dues gets a very strong reaction at the minute - I think they just like all the sass that comes from that song."

Inspired by that success, the singer has not one but two new albums cooking on the stove. She'll head back to the studio after wrapping up her tour this autumn, but can't confirm when the music will see the light of day.

"After all these years, the music industry is still a mystery," she says.

"It's still a mystery, and it's always like, 'Don't worry, you have plenty of time… Hurry up. We need it tomorrow'."