Sir Elton John, Kylie Minogue and Sir Paul McCartney are among the stars getting ready to perform for Queen Elizabeth II as she celebrates her Diamond Jubilee.
The musicians will play on a specially-constructed stage built around the Queen Victoria Memorial outside Buckingham Palace in London.
The show starts at 19:30 BST and will be broadcast on BBC One.
It closes three hours later as the Queen lights the National Beacon, the last of 4,180 beacons around the world.
Acts including Stevie Wonder and Jolls Holland have been running through sound checks ahead of the event.
Other artists taking part in the show include Jessie J, JLS, Robbie Williams, Dame Shirley Bassey, Ed Sheeran, Madness and Sir Cliff Richard.
Classical music will be represented by the BBC Concert Orchestra, Bryn Terfel and pianist Lang Lang. (PLS)