Anxious wait as Sarah wins over Oliver! Judges.
The Cardiff performer drew comparisons with West End legend Elaine Paige and Hollywood star Meryl Streep with her first live TV performance on Saturday.
But Sarah was the last contestant to learn she was through - narrowly avoiding a tense sing-off to book her place in next Saturday's programme.
She tearfully said: "Thank you, thank you!" as her ecstatic family - mum Bev, 47, dad Billy, 54, and brother David, who turned 11 on Friday - celebrated wearing T-shirts bearing Sarah's name and picture.
Millions of viewers saw former Cardiff High School pupil Sarah, from Roath, battle it out with the 11 other hopefuls vying for the role of Nancy in an Andrew Lloyd Webber-backed West End production of Oliver!
Wearing a sky blue dress, she performed an emotional version of Oleta Adams' Get Here.
Speaking on the live show hosted by GrahamNorton, the 25-year-old said: "To be a leading lady in a West End show is everything I have ever wanted.
"My fear will always be how young I look. When I was 18 I was playing a 12-year-old in Witches of Eastwick.
"This is the first time I've got anywhere near a character without a baby face. Forget the baby face, think about Sarah Lark the woman!"
PLEASED Sarah Lark is through to the next round of I'd Do Anything. Left, Sarah's mum and dad and her brother David were there to support her.