With 51 shopping days still to go, the Christmas lights in Oxford Street and Regent Street were switched on simultaneously for the first time.

Let there be light: Jim Carrey does the switch on

The lights also came on at St Paul's Cathedral, and its choir led thousands of people to smash the world record for mass carol singing.

The big switch-on: lights went on at the cathedral

Gallery: Stars switch on London's Christmas lights

The events coincided with a star-studded premiere of Disney's 3D A Christmas Carol in Leicester Square, with its stars Jim Carrey, Colin Firth and Bob Hoskins switching on the film-themed lights at the three locations after crowds were entertained with free concerts.

Light music: X Factor's Jedward at A Christmas Carol premiere

Carrey, who voices Scrooge and other characters in the animated film, flicked the switch at Oxford Street after the cast of musical Sister Act and girl group The Saturdays performed. In Regent Street, The Noisettes and Daniel Merriweather were among the entertainers before Firth pressed the red button.

Light up: Oxford Street gets in the Christmas mood

Gallery: A Christmas Carol premiere

At exactly the same time, St Paul's Cathedral was bathed in blue, green and pink floodlights for its Christmas illuminations, with Hoskins doing the honours after Little Boots and Spandau Ballet performed.

Razzle dazzle: Regent Street is sparkling/p>

The choir led more than 14,000 people at four sites for a record-breaking rendition of O Come All Ye Faithful.

Entertainment: Little Boots sings at St Paul's