It is a breathtaking version of the track and just shows what her voice is capable of,' said a source close to Susan.

The 48-year-old Susan has been working at a secret London location in a bid to be on course to release an LP before the end of the year.

She sifted through 350-400 possible tunes and has vowed to make her album appeal to as wide an audience as possible.

'We're not going to throw out some souvenir album of show tunes. She's going to surprise a lot of people with this record,' said her mentor Simon Cowell.