Katie Melua and Eva Cassidy get the first position on UK Chart with a version of the classic Louis Armstrong song "What a Wonderful World".

Singer Katie Melua and the late Eva Cassidy topped the UK singles chart on Sunday with a version of the classic Louis Armstrong song "What a Wonderful World".

Their charity duet knocked "Bleeding Love" by last year's "X Factor" winner Leona Lewis from the number one spot after seven weeks, according to the Official UK Charts Company.

Cassidy, who died of cancer in 1996, is Melua's musical idol. Money raised by their duet goes to the British Red Cross.

Bookmaker William Hill said the song is its third favourite to secure the Christmas number one, behind this year's "X Factor" winner Leon Jackson and Lewis.

American rapper Soulja Boy Tell 'Em climbed seven places to number three with "Crank That (Soulja Boy)", a former U.S. number one.

Up four places at number four was Mariah Carey with "All I Want For Christmas Is You", while Girls Aloud slipped to fifth with "Call the Shots".

American producer and rapper Timbaland's "Apologize" fell two spots to number six. Also down were Take That with "Rule the World" at seven.

The classic Christmas song "Fairytale of New York", by The Pogues and Kirsty MacColl, climbed four places to number eight, while "Heartbroken" by British producer T2 and singer Jodie Aysha slipped to ninth.

Completing the top 10 were dance act Cascada with "What Hurts the Most".