Thousands sing 'Happy Birthday' to Queen Elizabeth II

Britain's Queen Elizabeth II, surrounded by members of the royal family, takes her seat at the Royal Albert Hall in London on Saturday April 21, 2018, for a concert to celebrate the 92nd birthday of Queen Elizabeth II. (John Stillwell/Pool via AP)

LONDON (AP) — The audience at Royal Albert Hall got a rare treat Saturday — the chance to sing "Happy Birthday" to the longest reigning monarch in British history.

Queen Elizabeth II, with her eldest son Prince Charles at her side, waved to the crowd as they celebrated her 92nd birthday in song.

Charles got an enthusiastic response when he introduced her as: "Your majesty, mummy."

Queen Elizabeth II and the Prince Charles stand with performers on stage at at the Royal Albert Hall in London on Saturday April 21, 2018, for a concert to celebrate the 92nd birthday of Britain's Queen Elizabeth II. (Andrew Parsons/Pool via AP)

The queen took center stage after a varied pop concert featuring British singers Sting, Tom Jones and Jamie Cullum along with Australian star Kylie Minogue, long a fan favorite here.

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.

Sting and Shaggy perform at the Royal Albert Hall in London on Saturday April 21, 2018, for a concert to celebrate the 92nd birthday of Britain's Queen Elizabeth II. (Andrew Parsons/Pool via AP)

She was flanked in the royal box by Charles, heir to the throne, and Prince William, next in the line of succession.

Prince Harry and fiancee Meghan Markle also attended, generating a roar of applause when they took their seats. The couple will wed May 19 at Windsor Castle.

Britain's Prince Harry and Meghan Markle arrive at the Royal Albert Hall in London to attend a concert to celebrate her 92nd birthday, Saturday April 21, 2018. (John Stillwell/Pool via AP)

Prince William's wife Kate, the Duchess of Cambridge, did not attend. She is expecting the couple's third child.

The queen's husband, Prince Philip, was also missing. He is recovering from hip replacement surgery.

Kylie Minogue performs at the Royal Albert Hall in London on Saturday April 21, 2018, for a concert to celebrate the 92nd birthday of Britain's Queen Elizabeth II. (Andrew Parsons/Pool via AP)

The show featured contemporary tunes, but included songs from earlier eras, including selections from "My Fair Lady" — one of the queen's favorites — and a sentimental rendering of "Wonderful World."

Earlier in the day, honorary gun salutes were staged at Hyde Park, the Tower of London, a castle in Wales and the town of Windsor to mark the occasion.

In this Ministry of Defence photo dated Saturday 21, 2018, army reservists from C Troop 211 Battery, which forms part of 104 Regiment Royal Artillery, fire a 21-gun salute inside the grounds of Cardiff Castle, Wales, to celebrate Queen Elizabeth II's 92nd birthday. (Corporal Tom Evans (RLC)/Minstry of Defence via AP)

The queen celebrates two birthdays every year: Her actual birthday on April 21, which she usually marks privately with her family, and her "official birthday" in the summer. That usually falls on the second Saturday in June, when she joins the Trooping the Color military parade in central London.

Elizabeth's real birthday this year came on the tails of the Commonwealth Heads of Government meeting, which brought the leaders of the 53 Commonwealth countries together in England.