Lee Ryan will sing hit single Army of Lovers

The former member of boy band Blue also performed alongside 80s pop group Bananarama at the event.

The cast from West End shows Mama Mia and Scrooge, which opens at the London Palladium on Monday, also performed.

The party, based on the theme of CGI film Ice Age 2 - The Meltdown, took place on Saturday afternoon.

Children were also able to hunt for acorns hidden in Regent Street shops to win the chance to hold a premiere party for 50 friends at a private screening room in Soho, central London.

This year marks the 51st anniversary of the festive lights on one of London's busiest shopping streets, and for the first time a fireworks display accompanied the switch-on.

Lee Ryan joins a long list of celebrities who have turned on the famous lights.

Previous stars to have pressed the button include Joan Collins (in 1985), Kylie Minogue (1989), Sir Anthony Hopkins (1992), All Saints (1998), Will Young (2002) and pop-rock act Busted last year.