The event was a break from tradition as the Queen usually celebrates her actual birthday in private.
"Mummy", he called her.
Shaggy and Craig David also performed, and the festivities took a long stroll down memory lane, with audio from a speech Elizabeth made on her 21st birthday and video from her Golden Jubilee, when roughly 1 million people gathered outside Buckingham Palace to honor her.
Members of the royal family who were in attendance included Camilla, Duchess of Cornwall, Prince Charles, Prince of Wales, Prince William, Duke of Cambridge, Princess Anne, Princess Royal. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed. The Queen gave them a bit of a wave to acknowledge them, but tutted and rolled her eyes when he switched to the less formal "Mummy". Prince Harry and Meghan Markle seemed to be delighted though, but maybe that's just the almost-married glow.
The couple, who will Wednesday on May 19, looked happily in love at the event.
Prince William and Kate Middleton were not seen at the birthday concert as Kate is expecting a third child. He is recovering from hip replacement surgery.
The trio took to the stage to perform a version of the George Formby classic, who is believed to be the Queen's "favourite" singer.
As is customary with monarch's birthdays, soldiers from the King's Troop Royal Horse Artillery and the Honourable Artillery Company fired gun salutes in London's Hyde Park and the Tower of London earlier on Saturday.
While events were held nationwide to celebrate the Queen's 90th birthday, Elizabeth II usually prefers to spend her birthday in private.
She later joined Prince Charles on stage for the show's climax and was presented with a gift by a boy named Mason from west London, who was also celebrating his birthday.