The jubilee was being marked around the world in members of the 54-nation Commonwealth of former British colonies.
The small Pacific island nation of Tonga claimed the honor of lighting the first of more than 4,200 commemorative beacons to be set alight in Britain and abroad. The queen will light the final beacon following the concert.
One beacon will be lit in Kenya at the Treetops Hotel, where Elizabeth was informed of her father's death in 1952, making her the queen.
Margaret Watson, 73, in the crowd near Buckingham Palace on Monday, remembered watching the Coronation on the television set which her family bought especially to watch the event.
"I am here to say thank you to the queen for all she has done," said Watson, who came to London from Yorkshire in northern England with family members. "I am just so pleased to have lived through her reign."
Associated Press Writer Robert Barr contributed to this report.
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