She's bigger than Elvis and the Beatles and worth a mint. But who is Hannah Montana?

Squeaky clean, just 15, and billed as the anti-Britney superstar, Miley's the next big thing

This 15-year-old is worth £7m. Her TV show is watched by seven out of 10 American children. Its soundtrack went quadruple platinum and her tour sold out in minutes. Tickets to see her live sell for up to £1,200. Her favourite colour tic tac is green and purple.

This may all come as news to you, but children and (some) parents know all of this and more about Miley Cyrus, aka Miley Stewart, aka Hannah Montana. The other half of the population has never heard of her. She is the latest tween sensation, brought to you by the Disney channel and now showing in 3D at a cinema near you. She is, like, totally massive. And also nang, say the nation's pre-teens.

Miley/Miley/Hannah is a tangled, post-modern phenomenon. Miley Cyrus is an actress and singer, daughter of the "Achy Breaky Heart" singer Billy Ray. Miley Stewart is the ordinary 14- year-old schoolgirl she plays in Disney's teen drama, Hannah Montana. Hannah is the pop star whom Miley Stewart secretly turns into in her spare time, donning a blonde wig and a can-do attitude. You follow all this so far?

It's the crossover appeal that has turned Miley into a multimedia success. As well as playing Miley in the TV series and the movie, Hannah Montana & Miley Cyrus: Best of Both Worlds Concert, Miley Cyrus sings the theme tune. Her UK concerts saw fans queuing from 5am and she had five singles in the US Top 100 simultaneously – more than the Beatles or Elvis Presley.

A range of Miley merchandise goes from dolls (£19.99) to LCD TVs (£199) and games on Nintendo Wii. And just to make things even more confusing, Miley's on-screen dad is played by Miley's real dad, Billy Ray.

Miley herself remains teeth-grindingly upbeat about the fame game. "All I want to do is have an impact around the world," she says, emphasising that her faith keeps her grounded. "That's kind of why I'm in Hollywood: to be like a light, a testimony to... God". Miley is already being billed as the anti-Britney – the child star who will manage to emerge unscathed. She has promised to eschew booze, drugs and sex before marriage. "Doing those sorts of things will only make you feel good for so long, but friends and family will make you feel awesome for ever!"

There is just one crack in this wholesome image: a dark compulsion that may yet prove fatal to Miley's career. "It's my favourite thing in the world," she has confessed: "I'm addicted to ketchup. I drink ketchup." Beware.