The Queen's military band surprised passing tourists on Tuesday with a medley of Michael Jackson songs.
Guards outside Buckingham Palace struck up the hit tune Heal The World, which was the final number of the king of pop's emotional memorial service.
Then soldiers marched in time as the bass line to Bad blasted out, with onlookers singing along and whistling.
As the tribute took place the monarch was hosting her second garden party of the season amid bright sunshine.
Just a week ago hail stones had guests running for cover as torrential rain washed out the first royal tea party of the summer.
Elegant in a fuchsia pink ensemble, the royal mingled with guests tucking into cakes and sandwiches.
"I've waited a lifetime to be here and to see the Queen is a great honour," said one lucky invitee.
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