Queen Elizabeth II stepped gingerly onto the Buckingham Palace balcony Thursday, drawing wild cheers from the tens of thousands who came to join her at the start of four days of celebrations of her 70 years on the throne.

Her fans sported Union Jack flags, party hats or plastic tiaras. Some had camped overnight in hopes of glimpsing the 96-year-old queen, whose appearances are becoming rare, and a chance to watch the Trooping the Color — a military parade that has marked each sovereign’s official birthday since 1760.

It was an explosion of joy in the massive crowd, one of the first big gatherings in the U.K. since the COVID-19 pandemic began.

“Everybody has got the same mission,” said Hillary Mathews, 70, who had come from Hertfordshire, outside London. “All the horrors that’s been going on in the world and in England at the moment are put behind us for a day, and we can just enjoy really celebrating the queen.”

Elizabeth, who became queen at 25, is Britain’s longest-reigning monarch and the first to reach the milestone of seven decades on the throne.

Also read: Not just any cake: A Bollywood homage to queen for Jubilee

Yet after a lifetime of good health, age has begun to catch up with her. Buckingham Palace announced late Thursday that the queen would not attend a thanksgiving church service Friday after experiencing “some discomfort” at events on Thursday. The palace said with “great reluctance” the monarch has decided to skip the service at St. Paul’s Cathedral.

The queen has had trouble moving around in recent months, and has pulled out of many public events.

But Elizabeth took part Thursday night in lighting a chain of ceremonial beacons at Windsor Castle as planned.

The Jubilee celebrations go on for a long weekend, and it was not immediately known how the news would affect Jubilee events on Saturday and Sunday.

The palace says “the queen greatly enjoyed" Thursday's events — and it showed.

She basked in her moment. Smiling, she chatted with her great-grandson Prince Louis, 4, who occasionally covered his ears as 70 military aircraft old and new swooped low over the palace to salute the queen. The six-minute display included a formation of Typhoon fighter jets flying in the shape of the number 70.

The queen, wearing a dusky dove blue dress designed by Angela Kelly, was joined on the balcony by more than a dozen royals — though not Prince Harry and his wife Meghan, who gave up front-line royal duties two years ago. The couple traveled to London from their home in California with their two young children to take a low-key part in the celebrations, and watched Thursday’s Trooping the Color with other members of the family.

They did not appear on the palace balcony, because the monarch decided that only working members of the royal family should have that honor. The decision also, handily, excluded Prince Andrew, who stepped away from public duties amid controversy over his links with the convicted sex offender Jeffrey Epstein.

Andrew will also miss Friday's service of thanksgiving after testing positive for COVID-19.

The jubilee is being commemorated with a four-day holiday extravaganza and events including a concert at Buckingham Palace on Saturday and a pageant staged by thousands of performers drawn from schools and community groups around the country on Sunday. Thousands of street parties are planned nationwide, repeating a tradition that began with the queen’s coronation in 1953.

Also read: Queen Elizabeth II’s extraordinary life and reign

Not everyone in Britain is celebrating. Many people have taken advantage of the long weekend to go on vacation. And 12 protesters were arrested Thursday after getting past barriers and onto the parade route. The group Animal Rebellion claimed responsibility, saying the protesters were “demanding that royal land is reclaimed.”

Yet the jubilee is giving many people — even those indifferent to the monarchy — a chance to reflect on the state of the nation and the huge changes that have taken place during Elizabeth’s reign.

Former Prime Minister John Major, one of the 14 prime ministers during the queen’s reign, said the monarch’s stoic presence had helped steer the country over the decades.

“The queen has represented our better selves for over 70 years,” he told the BBC.

In a written jubilee message, the queen thanked people in Britain and across the Commonwealth involved in organizing the celebrations. This country does like a good party.

“I know that many happy memories will be created at these festive occasions,” Elizabeth said. “I continue to be inspired by the goodwill shown to me, and hope that the coming days will provide an opportunity to reflect on all that has been achieved during the last 70 years, as we look to the future with confidence and enthusiasm.”

Congratulations arrived from world leaders, including U.S. President Joe Biden and Pope Francis. French President Emmanuel Macron called Elizabeth “the golden thread that binds our two countries” and former President Barack Obama recalled the queen’s “grace and generosity” during his first visit to the palace.

“Your life has been a gift, not just to the United Kingdom but to the world,” Obama told the BBC “May the light of your crown continue to reign supreme.”

Cheers and the clop of hooves rang out Thursday as horse-drawn carriages carried members of the royal family, including Prince William’s wife, Kate, and their children Prince George, 8, Princess Charlotte, 7, and 4-year-old Prince Louis, from Buckingham Palace to Horse Guards Parade, a ceremonial parade ground about 1 kilometer (0.6 miles) away, for the Trooping the Color ceremony.

The annual tradition is a ceremonial reenactment of the way battle flags, or colors, were once displayed for soldiers to make sure they would recognize a crucial rallying point if they became disoriented in combat.

Prince Charles, the 73-year-old heir to the throne, played a key role during the event Thursday as he stood in for his mother — as he has more and more of late.

Clad in his ceremonial military uniform, Charles rode onto the parade ground on horseback and took the salute of the passing troops in their scarlet tunics and bearskin hats. He was flanked by his sister, Princess Anne, and oldest son Prince William.

Tens of thousands of locals and tourists lined the route between palace and parade ground to take in the spectacle and the atmosphere.

“I was right at the front ... I’m very proud of the queen,″ said Celia Lourd, 60. "She’s been my queen all my life and I think we owe her an awful lot for the service she’s given to the country. So I wanted to come to show my support today and say thank you.”