The Queen has pulled out of an upcoming event in her platinum jubilee celebrations after appearing on the Buckingham Palace balcony with working royals to watch the opening military flypast.

The beaming 96-year-old monarch had appeared delighted at the display of roaring RAF jets flying in the formation of the number ’70’, which was followed by the Red Arrows filling the sky with blue, white and red.

The Trooping the Colour parade drew huge crowds to central London and marked the start of four days of festivities, which will be followed by a special service of thanksgiving at St Paul’s Cathedral on Friday (local time).

But in breaking news, the palace announced the Queen would not be attending Friday’s thanksgiving service after experiencing “discomfort” at the parade.

A statement from Buckingham Palace said the “journey” and “activity” that would be required of the Queen to participate had led to the decision not to attend.

“The Queen greatly enjoyed today’s birthday parade and flypast but did experience some discomfort,” said the statement.

“Taking into account the journey and activity required to participate in tomorrow’s national service of thanksgiving at St Paul’s Cathedral, Her Majesty with great reluctance has concluded that she will not attend.

“The Queen is looking forward to participating in tonight’s beacon lighting event at Windsor Castle and would like to thank all those who made today such a memorable occasion.”

The Queen led the beacon event to finish Thursday’s celebrations, lighting the principal beacon at her Windsor Castle home.

Eurofighter Typhoons of the Royal Air Force fly over London in a 70 formation. Photo: Getty

The Queen’s involvement in this year’s celebrations will be somewhat limited compared with previous major events.

In recent months the Queen has cut back public appearances due to what Buckingham Palace calls “episodic mobility issues”. In May, she missed the opening of parliament for the first time in almost six decades.

Senior royals, including Charles, and his eldest son William, 39, are carrying out some ceremonial duties on the Queen’s behalf.

Another royal who won’t attend the thanksgiving service is Prince Andrew, who has tested positive for COVID.

Meanwhile, Prince Harry and Meghan Markle have maintained a low profile, seemingly not to attract headline attention. They were spotted looking relaxed as they watched Thursday’s festivities from a building overlooking the parade ground.

Millions of people across Britain and the world were expected to watch the celebrations, join street parties and light beacons in honour of the long-reigning monarch.

Holding a walking stick and wearing a dusky dove blue outfit, the Queen was joined by her son and heir Prince Charles, 73, and other senior royals on the balcony of Buckingham Palace.

While the family waved to the crowds and enjoyed a Royal Air force fly-past, Louis – Prince William’s four-year-old son – covered his ears and howled as the planes roared overhead.

Prince Louis stole the show as the royals watched the air displays from the balcony. Photo: Getty

World leaders, including Australian Prime Minister Anthony Albanese, US President Joe Biden, France’s Emmanuel Macron, Pope Francis and former British PMs, were among those sending messages of goodwill.

The celebrations began with the Trooping the Colour, a military parade held annually to mark the Queen’s official birthday. It featured 1500 soldiers marching to military music in ceremonial uniforms of scarlet tunics and bearskin hats.

Later the crowds moved to the Mall, the grand boulevard running up to Buckingham Palace. In brilliant sunshine, they cheered and waved Union flags while modern and historic planes flew overhead.

Trooping The Colour is a military ceremony performed by regiments of the British Army. Photo: Getty

Thursday marked not only the start of the jubilee, but also the 69th anniversary of the coronation of the Queen, who became monarch on the death of her father George VI in February 1952.

There were artillery gun salutes in London, across the United Kingdom and from Royal Navy ships at sea.

“It was lovely, everything we hoped it would be. We’re a bit older now, so we were here for the 25th and then the 50th [jubilee]. But this was the best one,” said nurse Ian Higgins, 62, among the crowd in central London.

The government announced two public holidays to mark the celebration, which is the first major public gathering since the pandemic and a welcome distraction for many at a time of growing economic hardship.

Londoners gather in Trafalgar Square to celebrate from afar. Photo: Getty

Among the tributes pouring in from around the world was a video message from former US president Barack Obama that was broadcast on the BBC.

“Your life has been a gift, not just for the United Kingdom, but for the world. And it is with gratitude for your leadership and the kindness that you’ve shown me and my family that I say, may the light of your crown continue to reign supreme,” he said.

A number of people caused a brief disturbance by running out in front of marching soldiers on the Mall boulevard before they were dragged away by police. Several were arrested.

Australia lights up for the Queen

The Sydney Harbour Bridge is lit in Royal Purple. Photo: AAP

Mr Albanese also paid tribute to the Queen, saying she has been a good friend of Australia.

In a speech marking her 70-year reign, the Prime Minister said the monarch was a show of stability throughout her many decades on the throne.

“The Queen has been a rare constant, an enduring, inspiring, growing presence of calm, decency and strength,” he said at a ceremony in Canberra on Thursday night.

“Australians hold Queen Elizabeth in respect and affection, even as the bond between our nations is no longer what it was at the dawn of her reign.

“No longer parent and young upstart. We stand as equals, more importantly, we stand as friends.”

Mr Albanese then lit a beacon, one of 1500 being lit across the Commonwealth in honour of the celebrations.

Canberra’s Aspen Island on Lake Burley Griffin will be officially renamed in honour of the Queen.

Landmarks across the country, including Parliament House and the Sydney Opera House, were lit up in royal purple.

Mr Albanese also used his speech to recount how his own birth was delayed due to one of the Queen’s visits to Australia.

“My mother insisted on seeing the tribute to Queen Elizabeth on her way to hospital,” he said.

“She insisted on going via the city to ensure that she saw all of the commemoration that was here at the time.”

-with AAP