Jai McDowall victory defies the 'Simon Cowell factor'

Jai, 24, from Tarbolton in Ayrshire, had been dubbed the dark horse in the show, but he was widely expected to be pipped to the top spot by 12-year-old favourite Ronan Parke.

Instead, the Scots care worker was voted the winner following a public vote on the show, with his young Justin Bieber lookalike rival coming in second. Jai secured 2.5 per cent more votes.

Jai is the first Scot to have won the talent show. Susan Boyle was previously runner-up in 2009, narrowly missing out on the top spot to dance troupe Diversity before going on to become a global recording sensation.

A 100,000 prize is now Jai's and he will perform at the Royal Variety Show in front of an audience including the Queen.

The Scot, who had said he would pay off his parents' mortgage with the winnings, had received a standing ovation following his rendition of To Where You Are by Josh Groban.

On hearing the result, he told the show's hosts, Ant and Dec: "I feel absolutely amazing, fantastic."

Although clearly surprised by the result, judge Simon Cowell called Jai a "worthy winner" and fellow judge Amanda Holden said she was "thrilled" for the upcoming star.

Ronan, who had been the subject of a smear campaign by an anonymous blogger who claimed he was already signed to Cowell's label, gracefully congratulated his competitor. The schoolboy is widely expected to be offered his own recording contract, with industry insiders predicting stellar success in the teenybop pop market.

Jackson Five soundalikes New Bounce finished in third place.

Prior to his winning performance, Jai, who had previously made it to boot camp on reality singing show X Factor, sang a version of Evanescence's hit Bring Me To Life. At his original audition in Glasgow he performed Anthem from Chess.

Following Jai's win, Cowell said: "We said tonight there was going to be a shock result. He wasn't one of the favourites coming in, but tonight we could feel he nailed the song. He came in believing that he could win and I think he's a worthy winner."

Cowell had been furious at the suggestion that he had been grooming Parke, calling in police to investigate the source of the allegation.

After his performance on the night, Cowell told the nervous singer: "Jai this was very well timed, this was you at your best. For the first time I saw you come out on stage believing like you could win. Jai, I don't think the vocal was perfect, it was a little bit monotone, but it was still terrific.."

David Hasselhoff added: "Jai, you sang beautifully. It looked like half of Scotland was here."

Lynsey O'Donnell, a barmaid at The Plough Inn in Tarbolton, where McDowall used to work and sing karaoke, paid tribute to her friend. She said: "I've known Jai for about 20 years now and he's such a lovely lad. Everyone from the village has been behind him since the start.

"We're all absolutely ecstatic – the whole village is out in force celebrating. Jai has been singing here for about 10 years and when he turned 18 he got a job serving behind the bar.

"He's popular with everyone and we've all loved having him sing karaoke."

A lover of musicals, Jai previously told the audience he was flattered by a comparison to Boyle and said that he would be delighted if he could experience even half of her success. Jai cites his father, who has played in numerous local bands throughout the years, as his number one inspiration.

Boyle, from Blackburn, East Lothian, was favourite to win the show in 2009 but was named runner-up in an equally shock result.

The singer has gone on to make tens of million of pounds and has seen worldwide success.

Her first album was released in November 2009 and debuted as the number one best-selling CD on charts around the globe.

Boyle was officially recognised by Guinness World Records as having had the fastest selling debut album by a UK female artist.