Catherine, Princess of Wales, joins the royal family on the palace balcony, capping her first public appearance since being diagnosed with cancer

The Shopping Centre, London
CNN
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Catherine, Princess of Wales, joined other members of the British royal family on the balcony of Buckingham Palace for the king's official birthday, capping her first public appearance since being diagnosed with cancer.

The Princess of Wales, her husband William, their children George, Charlotte and Louis gathered with King Charles and Queen Camilla to watch a Royal Air Force flypast. They waved and smiled to the crowd, who responded with cheers.

The Princess, also known as Kate, had earlier been driven in a state carriage with her children from Buckingham Palace to Horse Guards Parade to attend the celebration, known as Trooping the Colour. She could be seen wearing an Irish Guards regimental pin, a nod to her role as honorary colonel.

The family were then seen watching the events from a vantage point, while Kate's husband William, Prince of Wales, rode his horse.

For Kate, it was her first public appearance since Christmas Day, weeks before her cancer diagnosis.

Kate left public duties in January, following what Kensington Palace said at the time was surgery for a non-cancerous abdominal condition. In March, amid speculation about her well-being, she revealed that she had been diagnosed with cancer after surgery and was undergoing treatment.

King Charles III and Queen Camilla were also taken by horse-drawn carriage from Buckingham Palace, drawing cheers from the packed crowd as they slowly made their way up the mall. The king participated this year in a carriage rather than on horseback due to his own cancer diagnosis.

People of all ages gathered throughout the mall for the event. Some spectators wear Union Jack hats and fascinators, while others wave flags. Some sang the national anthem.

Kate gave an update on her health on Friday, saying she has made good progress in her recovery. But she said she expected her treatment to last a few more months and she wasn't out of the woods yet.

Trooping the Color is a magnificent military spectacle which sees 1,400 officers and soldiers, along with 400 musicians and 200 horses, parade through the streets of London, from Buckingham Palace to the Horse Guards Parade, while crowds line the route.

The event – one of the highlights of the royal calendar – has been a tradition marking the official birthday of the British sovereign for more than 260 years. However, Charles' real birthday is in November.

Britain's kings and queens have doubled down on their festivities since the 18th century, holding both a public celebration of the official birthday and a more private event on the actual date.

This tradition is believed to have started with party-crazed King George II in 1748. Like Charles III, George was born in November, when the British weather is often less than ideal.

Proof of this is that the weather deteriorated as the events drew to a close. Crowds awaiting the king's return to the palace were lashed by heavy rain and gusty winds. Some spectators had difficulty keeping their umbrellas in place.

Speaking about Kate's balcony appearance, David Betteridge, 66, told CNN she looked good, so hopefully that's a good sign.

It's really nice to see her again actually, he added. Most of the time we stayed dry. But we got really wet right after the ceremony, once the parade was over. It rained very hard.

Anna Yang, 30, who was on holiday in the UK from China, said she saw the flypast from her nearby hotel. It was great. This is the first time, even in our own country, that we see all the national planes crossing the skies, she told CNN. It was incredible.

But anti-royalists also showed up, some of whom chanted shame and not my king!

This year, procedures have been adapted as Charles, 75, continues treatment for an unspecified form of cancer.

Doctors have been encouraged by his progress, allowing him to return to public duty in April, but every engagement he makes is reviewed and adjusted as appropriate.

For Saturday's events, he carried out his review of the troops seated in an Ascot pram alongside Queen Camilla.

Three of the British Army horses that passed through London in April returned to duty and took part in this weekend's anniversary parade. The two remaining horses are enjoying a summer holiday in the Chilterns and will return to service in due course, according to the army.