Can Emma Watson hold on to the magic?

Hollywood history is littered with fallen child stars – but smart, savvy Emma Watson isn't about to join the list, says Alice-Azania Jarvis

In the annals of celebrity misdemeanour, it's hardly vintage incident. Rumours of a photo – topless, towel around her waist, standing next to a hot tub – emerged last week. Emma Watson, star of the Harry Potter films, was said to be "appalled" at the situation. "She is trying to seek out the source so she can put a stop to it," reported a breathless Daily Mail on the subject. "She says the picture has been faked."

By the standards of her Hollywood peers – the crotch-flashing Paris Hiltons and Britney Spearses, the rehab-frequenting Lindsay Lohans – it might not be much, but it was enough to cause headlines around the world. Why? Well, partly because the latest instalment in the Harry Potter series – Harry, Ron and Hermione's penultimate adventure – was just a fortnight away from release, and any news about the film's bankable young stars would be enough to ignite a fan frenzy. Much of the furore, though, was sparked by the story's subject. After all, this was Emma Watson: straight-A student, bonafide goodie-two-shoes, poster girl for all that is not hedonistic about Hollywood. By sheer coincidence, the freckle-faced girl from Oxford had just given a (marginally) racy interview to The Sun. "I wish I'd done more naughty things," she was quoted as saying. "I'm ready to start taking risks."

The picture is almost certainly a fake. Famous or no, it would take a certain strain of foolhardiness for a girl to pose semi-naked in this age of Twitpics and Facebook updates. It's a quality which Watson doesn't possess. In an interview with this month's Vogue (her face, pixieish and framed by newly-short haircut, adorns the front cover), she speaks of concerns about communal living: "One morning I was walking down the corridor from my bathroom in just a towel and I thought I must be mad, anyone could Tweet up my towel." No one did – though it's hardly the voice of someone who goes bathing in the buff.

This self-awareness, this sense of decorum, has defined Watson's rise to fame. In 1999, aged just nine years old, she won the role that would not just transform her into one of the most recognisable people on the planet, but would also ensure she would never need work again. Alongside a 10-year-old Daniel Radcliffe and a 12-year-old Rupert Grint, she was named as one of the three protagonists in the film adaptation of J K Rowling's multi-million pound series of children's books. Like her character, Hermione Granger, Watson was bushy-browed, thoughtful and principled.

Since then, her star has shown little sign of shrinking. Repeatedly singled out by reviewers for her on-screen dynamism, she has collected a cabinet (or several) full of awards. In 2005, she became the youngest person ever to appear on Teen Vogue's cover and, from 2007, her handprints adorned the walkway before Hollywood's Chinese Theatre. When her contract was renegotiated midway through the Potter series, her pay swelled from £1m to £2m per movie. Happily, in an era when bankability increases in accordance with good looks, Watson's adolescence was marked not by spots but by a physical blossoming: at the age of 19, she had a major modelling contract under her belt, gracing billboards across the world as the face of Burberry. This year, Vanity Fair named her Hollywood's highest-paid star, after she pulled in a staggering £19m.

What, it's worth asking, happens when such success, such celebrity is achieved so early in life? Hollywood has a tried-and-tested model for its young stars. More often than not it involves a period of public rebellion, accompanied by on-tap access to the trappings of the good life: parties, nightclubs, designer clothes and alcohol. Lindsay Lohan, in and out of jail, incapable of choosing a decent film role, has been the latest casualty of Young and Famous Syndrome. As the PR veteran Max Clifford says, "The transformation from child star to adult is incredibly difficult – one of the hardest." Before Lohan we had Drew Barrymore, Macaulay Culkin, Jack Wild, to name just a few.

But not Watson. Content with pocket money of £50 a month for the first 18 years of her life, she, on learning of her fortune from her father, enrolled in a money management course at Coutts. Determined to live as "normal" a life as possible, she persuaded the Harry Potter directors to allow her a year's break and headed away from the tabloids to the United States for university. There, she has said, she chose not to drink: "I was underage and it would have been disrespectful," she observed. She drives a Toyota Prius and shares her flat with friends. She is not, it's safe to say, in a hurry to spend that fortune.

In behaving so modestly, Watson follows in a different tradition of stardom. Not for her the well-worn ways of Lohan, Wild, et al, but instead the less-trodden path pursued by Natalie Portman and Jodie Foster, two child stars-cum-serious actresses she is said to admire. Like Watson, Portman is famously studious. She took time out of her career to attend Harvard and declared that "she would rather be smart than a movie star". Foster, meanwhile, attended Yale University and is fluent in several languages. Crucially, both had talent to deliver on-screen later in life. "There are so many people in the public realm who don't have any talent that when someone who does comes along, we take to them," says Clifford on this. "Emma is much liked and admired and is seen to be a very good actress. She has substance. That's the magic combination."

The flipside of all this is a reputation as something of a goody two-shoes – even a bit of a bore. Watson will never be edgy. She is unlikely to be cool or – when the madness of Pottermania has died down – to excite the same off-screen interest as her less predictable peers. But in an age of gossip bloggers and up-skirt shots, perhaps that's no bad thing. So long as the reviews remain rosy, Emma Watson may be on to a very good thing.

Growing up on screen: the varying careers of child stars

Jodie Foster

A pre-teen prostitute in 'Taxi Driver', Foster went on to study at the prestigious Yale University and carved out a career later in life, starring in 'The Silence of the Lambs' and 'Panic Room'.

Natalie Portman

After making her debut at 13 in 'Léon', Portman starred opposite Meryl Streep in 'The Seagull' and earned an Oscar nomination for her role in 'Closer'. She studied at Harvard.

Brooke Shields

By the age of 14, she had played a child prostitute in 'Pretty Baby', appeared on the cover of 'Vogue' and been named as the face of Calvin Klein. Her TV show 'Suddenly Susan' was a hit in the 1990s, but the more recent 'Lipstick Jungle' proved less successful.

Lindsay Lohan

After a string of children's films, Lohan achieved critical acclaim in Tina Fey's 2004 comedy 'Mean Girls'. Popular fascination with her taste for partying and shopping, as well as her yo-yoing weight and fast-paced love life soon eclipsed her on-screen presence.

Hayley Mills

Famed for her roles in 'Pollyanna' and 'The Parent Trap', Mills's career floundered when her contract with Disney expired. In 2000 she won a Theatre World Award for her performance in 'Suite in Two Keys'. She appears in ITV's 'Wild at Heart'.