Prince George and Princess Charlotte Join Royal Family for Platinum Jubilee Concert at the Palace

Queen Elizabeth is throwing the ultimate house party!

The 96-year-old monarch opened the doors of Buckingham Palace to 22,000 guests on Saturday for a star-studded "Platinum Party" celebrating the U.K. and Commonwealth's contributions to fashion, sports, the environment and music during her record-breaking 70-year reign.

The Queen herself did not attend the concert due to her ongoing "mobility issues." PEOPLE has confirmed that she will be watching the show on TV at home in Windsor Castle — but her absence didn't dampen the celebration.

Meghan Markle and Prince Harry also did not attend the festivities. The couple is spending the day privately as a family to celebrate their daughter Lilibet's first birthday.

Fresh off their first royal walkabout in Wales, Prince George and Princess Charlotte joined their parents Kate Middleton and Prince William in the royal box for the star-studded show, which opened with a humorous sketch featuring the Queen and Paddington Bear having tea! When Paddington Bear said he always had a sandwich on him, the Queen quipped, "So do I," and pulled one out of her handbag!

Other royal family members attending the show included Prince Charles and Camilla, Duchess of Cornwall; Prince Edward and Sophie, Countess of Wessex with their children Lady Louise and James, Viscount Severn; Princess Anne and Sir Timothy Laurence; Princess Beatrice and Edoardo Mapelli Mozzi; Princess Eugenie and Jack Brooksbank; Peter Phillips and his daughters; Zara and Mike Tindall; the Duke and Duchess of Gloucester; the Duke of Kent; Prince Michael and Princess Michael of Kent and Sarah Chatto and her family.

Curated by composer Andrew Lloyd Webber, the party got started with Queen + Adam Lambert performing a rousing rendition of "We Are the Champions" as Kate, William and the children waved Union Jack flags along with the crowd.

It is the second performance by Queen guitarist Brian May at the palace, following his historic appearance on the Palace roof at the Queen's Golden Jubilee Concert in 2002.

For more on the Queen's Platinum Jubilee, listen below to our daily podcast PEOPLE Every Day.

"Twenty years after playing The Queen's glorious Golden Jubilee, we're very happy to be invited again," May told the BBC ahead of the show. "There was a moment when I wondered… after Buckingham Palace roof where can you go?!"

Alongside May, the party features performances from Elton John, Alicia Keys, Hans Zimmer, Duran Duran, Andrea Bocelli and Diana Ross.

Lloyd Webber and Hamilton creator Lin-Manuel Miranda will also appear in a special performance featuring casts and special guests from The Phantom of The Opera, Hamilton, Six, The Lion King, and Joseph and The Amazing Technicolor Dreamcoat.

Sir David Attenborough, Dame Julie Andrews, David Beckham and U.S. Open tennis champion Emma Raducanu are among the celebrity hosts appearing onstage or via video.

"I have had the honor of meeting The Queen many times throughout my life, including when I was with my family," Diana Ross told the BBC ahead of the show, which featured three stages, linked by walkways, to create a 360-degree experience in front of Buckingham Palace and the Queen Victoria Memorial.

Alongside these are 70 columns of light representing each year of the monarch's seven-decade reign. An impressive light show also featured a corgi, the Queen's beloved dog breed.

Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more!

"Her Majesty has and continues to be such an incredible inspiration to so many across the world," added Ross. "I was absolutely delighted to receive an invitation to perform on such a momentous and historic occasion."

Rocker Rod Stewart also shared words of praise for the Queen: "Queen Elizabeth has given incredible service to the United Kingdom over the last 70 years.

"She has demonstrated to the world what a special person she is and how lucky we are to have her."

Both William and Charles gave moving speeches during the concert.

"While no one's grandmother thanks them for talking about their age, my own grandmother has been alive for nearly a century," William said. "In that time, mankind has benefited from unimaginable technological developments and scientific breakthroughs. And although those breakthroughs have increased our awareness of the impact humans have on our world, our planet has become more fragile. Today, in 2022 — as The Queen celebrates her Platinum Jubilee — the pressing need to protect and restore our planet has never been more urgent."

Charles, who took the stage alongside his wife Camilla, Duchess of Cornwall, opened by stating, "Your Majesty, Mummy. The scale of this evening's celebration – and the outpouring of warmth and affection over this whole Jubilee weekend – is our way of saying thank you – thank you from your family, the country, the Commonwealth, in fact the whole world."