Her meteoric rise from singer in a church choir to international celebrity has been portrayed as an overnight sensation. However, Susan Boyle, the church-going middle-aged spinster tipped to win Britain’s Got Talent, is a serial talent show failure who has been taught by a professional voice coach.

Last week, her singing teacher, Fred O’Neil, said that Boyle’s audition for ITV’s Britain’s Got Talent was her last throw of the dice, after a string of rejections by other talent shows. According to the coach, who tutored Boyle for several years, she had decided to abandon her dream of becoming a professional singer until he convinced her to take part.

Despite being cast as an ingenue by the show’s producers, the 47-year-old, from Blackburn, West Lothian, auditioned unsucessfully for My Kind of People, the talent show hosted by Michael Barrymore in the late 1990s.

According to friends, Boyle also attended an audition for The X Factor, but left after it became apparent that people were being chosen for their looks.

She sent demo tapes to a number of record labels without success and had recorded a version of Cry Me a River for a charity compilation CD in 1999 and attended the Edinburgh Acting School, appearing at the Edinburgh Fringe.

Boyle’s performance of I Dreamed a Dream, from Les Miserables, on Britain’s Got Talent has been watched 40m times on YouTube and has made her an international celebrity.

The singer, who has lived alone with her cat, Pebbles, since the death of her mother in 2007, has been feted by Demi Moore, the actress, and her husband, Ashton Kutcher, and appeared last week on Good Morning America. She has been interviewed for Larry King Live and invited to appear on The Oprah Winfrey Show.

Simon Cowell, who is behind The X Factor and Britain’s Got Talent, has predicted her debut album will go to number one in America, and she is expected to earn £3m this year.

According to O’Neil, a professional vocal coach based in Livingston, West Lothian, the adulation is a far cry from the rejections that almost convinced Boyle to abandon her dream of making it as a professional singer. O’Neil said he urged her Boyle to reconsider and to attend the audition for Britain’s Got Talent in Glasgow last year.

“She always had a vision of herself as a singer, but last year she told me she wasn’t going to sing any more,” he said.

“I remember a phone call late last year when she said she was too old and that it was a young person’s game.

“When I first heard her sing, it was obvious she had a naturally good voice and our work was to make sure it lasted a lifetime and that it was extended to its full capacity. That was her just gearing up, she can sing better than that.”

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