- King Charles III, who is also receiving treatment for cancer, inspected troops from a gold carriage, rather than on horseback.
- They emerged in golden carriages to a sea of mobile phones, with people desperate to catch a photograph of the royals through the windows.
Image: BBC/AGENCIES
Catherine, Princess of Wales has made her much-anticipated first public appearance of the year at the annual Trooping the Colour parade.
The princess, who is currently undergoing treatment for cancer, could be seen smiling and waving from the Buckingham Palace balcony at the end of a ceremony filled with pomp and pageantry.
King Charles III, who is also receiving treatment for cancer, inspected troops from a gold carriage, rather than on horseback.
Thousands watched on in the heavy rain to witness one of the biggest events in royal calendar.
There were cheers from the waiting crowd as they caught their first glimpse of Catherine and the King heading from Buckingham Palace to Horse Guards Parade.
They emerged in golden carriages to a sea of mobile phones, with people desperate to catch a photograph of the royals through the windows.
The princess was pictured smiling, sitting alongside her children Prince George, Prince Louis and Princess Charlotte - with six-year-old Louis giving a little wave to the crowd.
It was Catherine's first public appearance of the year, as she is currently undergoing chemotherapy treatment for cancer.
In a statement released on Friday, the princess said she was "not out of the woods yet", and had "good days and bad days", but was "looking forward to attending the King’s birthday parade this weekend with my family".
In a change from last year, she watched the ceremony from a balcony with her children, instead of joining other senior royals on a dais.
Louis danced along to a march by the Scots Guards, and was spotted yawning while watching the parade.
His sister, Charlotte, was seen wiping steam off their carriage's windows, as they were on their way back to Buckingham Palace.
The King, meanwhile, has only recently made a return to public duties himself, after being diagnosed with cancer in February.
But since the general election was called last month, the palace has postponed any engagements "which may appear to divert attention or distract from the election campaign".
He was joined by Queen Camilla, as the pair made their way to the event in a glass-sided carriage.
As it emerged from behind the Buckingham Palace gates, huge cheers could be heard from the watching crowd.
He inspected troops from within his carriage with the Queen by his side - last year he did so on horseback.
Prince William, Princess Anne and Prince Edward did still take to their horses, donning full military uniform as they took part in the parade.
Taking the lead in this year's ceremony, as the sovereign's escort, were the Irish Guards. That role is rotated between five different regiments of the Foot Guards.
During the parade, their flag was "trooped" through the ranks of soldiers.
Made up of troops from the UK, Ireland and the Commonwealth, it was described as "unique" by Sgt Michael Flood, one of the regiment's soldiers.
Meanwhile his colleague Gdsm Colati Kitione, who is from Fiji, said it was an "honour and a privilege" to be asked to take part.
The regiment's mascot - an Irish wolfhound named Seamus - also made an appearance during the parade.
As a serving Guardsman, he parades alongside a drummer, and was inspected alongside the other soldiers, before taking his place at the front of the regiment.
Back on parade today were three of the five horses of the household cavalry that bolted and ran through the streets of London in April.
One, Tennyson, featured in the Sovereign's Escort, while two others - Trojan and Vanquish - were part of the ceremonial guard for the official entrance to the palaces.
A 41-gun salute rang out from nearby Green Park, leading up to an RAF flypast over Buckingham Palace.
The Royal Family - including the King, Queen, William and Catherine - came out onto the balcony at the palace to take in the view.
As is tradition, the flypast finished with the Red Arrows acrobatic team flying overhead - leaving trails of red, white and blue in their wake.
Earlier in the day, the man in charge of the flypast - Air Vice-Marshall Mark Flewin - said he was "very confident" it would go ahead, despite the bad weather.
It was a grey and blustery day in central London for this year's Trooping the Colour - with heavy showers soaking the troops towards the end of the ceremony.
But that didn't stop people turning out in large numbers to witness the annual display of pomp and pageantry first-hand - and umbrellas could be seen lining the streets of The Mall, and in the stands at Horse Guards Parade.
Among those watching on in the stands was Prime Minister Rishi Sunak, who was spotted taking a photograph of the parade on his phone.
Trooping the Colour has been taking place for over 260 years, and has long been used to mark the official birthday of the British monarch - Saturday's parade was the King's second since taking the throne.
Anti-monarchy protesters from the group Republic could be seen scattered among those watching on.
They were waving big yellow flags reading 'Not My King', which seemed to make some of the parading horses jumpy.
In the days before the event, the Metropolitan Police banned the group from using amplified sound, but loud protest chants could be heard mixed in with cheers.