Actor Jim Carrey switches on the lights at Oxford Street
London's festive season is officially under way with the first co-ordinated switch-on of the capital's Christmas lights.
The lights in Regent Street and Oxford Street were turned on together for the first time.
And they were joined by celebrations in the City at St Paul's Cathedral.
The event on Tuesday was marked by street concerts and themed around the work of Charles Dickens.
The switch-on coincided with the world premiere of Disney's A Christmas Carol film at three cinemas in Leicester Square.
Dickens' Victorian morality tale, written in 1843, became one of the most popular and enduring works of all time, helping to popularise the notion of a traditional Christmas season.
Stars of the Disney film took part in the celebrations alongside acts from music and the theatre.
Actor Colin Firth at Regent Street for the Christmas lights switch-on
Actor Colin Firth led the switch-on in Regent Street and Hollywood's Jim Carrey lit up Oxford Street.
In the City, in the heart of Dickens' London, Bob Hoskins got the festivities under way at St Paul's Cathedral.
He was joined by opera singer Andrea Bocelli and the St Paul's Cathedral Choir in a world record gathering of carol singers.
Big screens relayed the record attempt to visitors in Regent Street and Oxford Street, where entertainment was provided by The Noisettes, Taio Cruz and the London Community Gospel Choir.
Other acts taking part in the joint switch-on included Spandau Ballet and Daniel Merriweather alongside performers from the West End musicals Hairspray and Sister Act.
This year's lights will be lit after dark each day until 6 January 2010.