UK X Factor winner Alexandra Burke was on hand to back a worthy cause and help set a new world record in London's Covent Garden on Sunday.

The singer played a surprise gig before joining TV presenter Jameela Jamil to host a successful record attempt for the most people to sign up as organ donors in one hour.

Alexandra performed her hit songs Hallelujah and Perfect, before encouraging members of the crowd to add their names to the donor register.

She was joined by young campaigners Hope Milne and Abby Thackray of the Battlefront organisation for the attempt which saw 321 sign-ups within 60 minutes.

A group of young people who have all received organ transplants later each released a heart-shaped balloon into the air to mark the end of the attempt.

The event had special resonance for Alexandra, whose own mother is currently awaiting a kidney transplant.

Talking after the event, she said: "You never know, my mum could even find a kidney through this today, it's just an amazing thing these girls have done."

To find out more about Battlefront campaigns, visit www.battlefront.co.uk