Emma Williams, from Halifax, was due to make her big stage debut today in the West End spectacular Chitty Chitty Bang Bang.

Emma, 18, a former pupil of Idle's Stage 84 stage school, has been hard rehearsing since landing the role of Truly Scrumptious.

And the young star was preparing to take her first bow tonight when the musical is unveiled to the public at a star-studded charity premiere, hosted by Roger Moore in aid of UNICEF and cerebral palsy charity SOS.

Emma stars opposite West End veteran Michael Ball who plays madcap investor Caractacus Potts in the show. Other big names in the musical are Brian Blessed as the dastardly Baron and Richard O'Brien as the evil Child Catcher.

Speaking to the Telegraph & Argus after the show's London launch last year, Emma said she was amazed when she was chosen ahead of thousands.

"I certainly didn't think I'd get the part - it's a world premiere and a huge show," she said.

"I'm prepared to tackle the fact that some people are going to recognise me now, but I'm not doing it for that, it's because I love the job.

"When Michael Ball took me down to the Palladium stage for the first time, I thought, 'Wow!' As soon as I put my foot on the stage, I welled up."

Emma joined Stage 84 when she was 12 and has played leading roles from Eliza in My Fair Lady to Anna in The King and I. Last summer, she starred opposite funnyman Steve Coogan in the British comedy The Parole Officer.

Chitty Chitty Bang Bang tells the story of Caractacus Potts who invents a flying car and then has to rescue his children from the clutches of the Baron.

In the stage version Emma takes on the role created by Sally Ann Howes in the film based on Ian Fleming's book.