At the annual Trooping the Colour procession, Catherine, Princess of Wales, made her much awaited first public appearance of the year.

After a lavish and extravagant ceremony, the princess—who is presently receiving cancer treatment—was spotted grinning and waving from the Buckingham Palace balcony.

Instead of riding a horse, King Charles III, who is also undergoing cancer treatment, rode in a carriage.

For one of the most important occasions on the royal calendar, thousands stood in the pouring rain.

As soon as the audience saw Catherine and the King leaving Buckingham Palace and making their way to Horse Guards Parade, they cheered.

A sea of cell phones greeted the carriage procession as spectators tried to get a picture of the royals through the windows.

The princess was seen grinning while seated with her kids, Prince George, Prince Louis, and Princess Charlotte. Louis, who is six years old, was seen waving to the audience.

The formal celebration, which has been going on for more than 260 years, honors the King’s official birthday.

Catherine had disclosed in March that she was receiving chemotherapy treatment for her cancer, and this was her first public appearance since Christmas.

The princess stated in a statement that she was “not out of the woods yet” and that she had “good days and bad days,” but that she was “looking forward to attending the King’s birthday parade this weekend with my family.” The message was made on Friday.

Unlike the previous year, she and her kids observed the ceremony from a balcony rather than joining other senior royals on a dais.

Louis was seen yawning as he watched the parade while dancing to a march led by the Scots Guards.

As they returned to Buckingham Palace in their carriage, his sister Charlotte was observed wiping steam from the windows.