Catherine, Princess of Wales attends the King's birthday celebration after revealing “good progress” in cancer treatment

The Mall, London
CNN
—

Catherine, Princess of Wales, arrived at Buckingham Palace for the King's official birthday parade, her first public appearance since revealing her cancer diagnosis.

The princess and her husband, Prince William, were seen driving to the palace together Color forces I started.

People of all ages gathered along the mall for this event. Some spectators wear Union Jack hats and necklaces, while others wave flags. The most patriotic were singing the national anthem.

The Princess of Wales – also known as Kate – will watch the rest of the show with her family nearby, and is expected to join her fellow royals on the balcony.

It marks a significant moment in the Princess's recovery, and is her first public appearance since Christmas Day – weeks before she was diagnosed with cancer.

Kate gave an update on her health on Friday, saying she had made “good progress” in her recovery. But she said she expects her treatment to continue for a few more months, and that she's “not out of the woods yet.”

King Charles III is also participating, despite undergoing treatment for cancer.

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

The event – one of the highlights of the royal calendar – has been an official birthday tradition for the British Sovereign for more than 260 years. However, Charles' actual birthday falls in November.

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

The tradition is believed to have begun with party-obsessed King George II in 1748. Like Charles III, George was born in November, when British weather is often far from ideal.

After the pageant, the parade returns to the palace where the king and family members traditionally gather on the famous balcony to greet cheering crowds of well-wishers below.

Kate's appearance was a big topic of discussion among onlookers as they chatted and warmed their hands with flasks of tea. “We are very excited,” Rene Geldenhuis, 41, told CNN.

She added: “We hope we can go up to the balcony and see her beautiful face again… We missed seeing her in public, so we are mostly here for her.”

In a slight change from his inaugural parade last year, King Charles will participate from a carriage rather than on horseback. He and Queen Camilla were taken in a carriage down the mall with other members of the royal family.

This year's procedures have been modified as the 75-year-old continues treatment for an unspecified type of cancer.

Doctors were encouraged by his progress, allowing him to do so Resume public facing duties in April, but each post he makes is reviewed and adapted where appropriate.

For the events on Saturday, he will be reviewing the troops sitting in the Ascot Landau carriage alongside Queen Camilla.

Three from the British Army Horses that galloped through London in April They are back on duty and are expected to take part in a Christmas parade this weekend. The remaining two horses are “enjoying a summer holiday in the Chilterns” and will return to duty in due course, according to the army.

This is a developing story and will be updated.