Emma Watson is "too busy" to go off the rails.

The 19-year-old 'Harry Potter' star - who shot to fame aged 11 playing brainbox student Hermione Granger in the wizarding franchise - insists the only reason she hasn't followed in the footsteps of other child stars and become embroiled in sex, drugs or alcohol scandals is because she works so hard.

She said: "I can totally understand why young actors go nuts. The level of interest in their lives, the pressure to be perfect - that's what you do, you screw up.

"I don't know why I haven't gone off the rails. I don't have time. I'm working too hard to be of the rebellious nature."

However, Emma hasn't ruled out letting her wild side come out in the future.

The actress added: "I'm sure when I hit my thirties I'll go crazy. I'll have this rush of hormones and Madness."