An estimated 20 million viewers are expected to tune in to watch the live final of ITV's talent contest.

Boyle, from the small town of Blackburn in West Lothian, Scotland, won international acclaim for her performance of I Dreamed a Dream, from Les Miserables, at her audition which aired in April on the first show.

The clip has been watched by millions of people on video-sharing site YouTube and she won praise from US actress Demi Moore who wrote about her on micro-blog Twitter.

Boyle faced criticism this week after being accused of a foul-mouthed rant while watching a semi-final at her hotel, which she denied, and was the topic of a blog by singer Lily Allen.

She has since been moved from the hotel in Wembley, north west London, where other competitors are staying and is living in a safe house with a close friend.

Despite this, 48-year-old Boyle remains favourite to beat the nine other remaining acts to win the show and pick up a £100,000 prize and the chance to sing at this year's Royal Variety Performance.

Speaking ahead of today's final show judge Piers Morgan claimed people were "trying to get inside her head", but said Boyle was looking forward to the final.

“Susan Boyle is a very, very nice lady from Scotland who never thought she would have this chance and she is really looking forward to it,” he told Sky News.

If she is to win, Boyle faces competition from two popular male street dance groups, Diversity and Flawless, who won praise from Morgan, and fellow judges Amanda Holden and Simon Cowell, for their energetic performances.

Among the acts in the final are 10-year-old Hollie Steel, who was allowed to sing twice after being overcome with nerves, grandfather and granddaughter singers 2 Grand and father-and-son dancing duo Stavros Flatley.

Scotland’s First Minister Alex Salmond has also backed Boyle to be successful and said she had the full support of the country.

“Susan Boyle has put her home town of Blackburn, West Lothian, well and truly on the map.

“Her outstanding performances in singing I Dreamed a Dream and Memory have catapulted her to global stardom.

“Over the past couple of months, Susan has wowed the judges and public with her incredible voice and display of enormous talent. I’ll be tuning in to cheer her on and I’m sure everyone in Scotland will be wishing her well.

“I’m convinced she’s got what it takes to be a winner in tonight’s final,' he said.

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