Prince William chatted with his uncle Prince Edward during the Order of the Garter procession this afternoon as they joined the King and Queen at Windsor Castle.
Charles and Camilla led members of the Royal Family to the annual Garter Day service at St George's Chapel as the busy royal summer period began in earnest.
Other royals at the traditional celebration commemorating the ancient Order of the Garter included Princess Anne and Edward's wife Sophie, Duchess of Edinburgh.
The King's appearance comes just two days after the Trooping the Colour ceremony in London where he was joined by fellow cancer patient the Princess of Wales. But Kate did not attend today's service, and her chemotherapy treatment continues.
Queues lasting more than two hours had built up outside the castle this morning, with visitors bringing camping chairs as they prepared for a long wait to get in.
While the main castle was shut to the public today, people queued to get a glimpse of those attending the service from 3pm at the chapel which is within the grounds.
Prince William was smiling as he arrived to attend the Order of the Garter service today
Prince William speaks to Prince Edward as they arrive at the Order of the Garter Service at St George's Chapel in Windsor Castle today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
Princess Anne, Prince Edward and Prince William at the Order of the Garter service today
The Prince of Wales and the Duchess of Edinburgh attend the annual Order of the Garter Service at St George's Chapel, Windsor Castle, Berkshire
Sophie, Duchess of Edinburgh arrives for the Order of the Garter service in Windsor today
Queen Camilla and King Charles III depart after the Order Of The Garter service today
Princess Anne and her husband Vice Admiral Sir Tim Laurence after today's service in Windsor
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Prince William waves to the crowd after attending the Order of the Garter service today
King Charles III and Queen Camilla attend the Order of the Garter service in Windsor today
Heralds during the Order of the Garter Service at Windsor Castle this afternoon
Princess Anne, Prince Edward and Prince William at the Order of the Garter service today
The Prince of Wales talking to The Duchess of Edinburgh after the service in Windsor today
King Charles III leaves St George's Chapel after the Order of the Garter service this afternoon
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Prince Edward and Prince William at the Order of the Garter service in Windsor today
Members of the Royal Family attend the Order Of The Garter Service at Windsor Castle today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Queen Camilla and King Charles III depart after the Order Of The Garter service today
Former prime minister Sir Tony Blair at the Order Of The Garter Service in Windsor today
King Charles III attends the Order of the Garter service at Windsor Castle on June 17, 2024
Shortly before 3pm this afternoon, the King donned heavy blue velvet robes and his ostrich-plumed hat as he headed the Order for the service after an annual lunch.
Watched by Sophie and Anne's husband Vice Admiral Sir Tim Laurence from the sidelines, the King, Queen, William, Anne and Edward made their way down to the Lower Ward in brilliant sunshine and blue skies.
Kate also normally attends to watch her husband, William, taking part.
But last week Kensington Palace confirmed that she would not be there this year due to her ongoing cancer treatment.
The beleaguered Duke of York - now a non-working royal - attended the lunch in his role as a Royal Knight Companion but, as last year, was not permitted to join the procession.
Andrew stepped down from public life after the furore over his friendship with convicted sex offender Jeffrey Epstein and paid millions to settle a civil sexual assault case with Virginia Giuffre, a woman he claimed never to have met.
Frail Princess Alexandra is a Royal Lady Companion but did not attend for 'her own comfort'.
At 2.45pm the grand procession began to make its way down to the chapel from the castle quadrangle before the service at 3pm.
It was headed by the Governor of Windsor Castle and the Military Knights of Windsor followed by heralds and then the knights of the order themselves including Sir John Major, Sir Tony Blair and Baroness Manningham-Buller.
As the King and Queen arrived at the door to the chapel, a fanfare of trumpets was played.
The Duke of Kent, also a Royal Knight Companion, was waiting in the chapel and did not take part in the procession - again because of his health.
However, Sophie and Vice Admiral Sir Tim both attended as guests.
Queen Camilla and King Charles III depart the Order Of The Garter Service at Windsor Castle on June 17, 2024
Princess Anne, Prince Edward and Prince William at the Order of the Garter service today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Prince William, Prince of Wales arrives to attend the Order of the Garter service, at St George's Chapel, at Windsor Castle, in Windsor, southern England, on June 17, 2024
King Charles III looks at Queen Camilla as they arrive for the Order of the Garter service today
Queen Camilla and King Charles III depart after the Order Of The Garter service today
The Duchess of Gloucester attends the Order of the Garter Service at Windsor Castle today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Former prime minister Sir John Major at the Order Of The Garter Service in Windsor today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Queen Camilla smiles as she arrives for the Order of the Garter service in Windsor today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
King Charles and Queen Camilla arrive for the Order of the Garter service in Windsor today
Earlier, the line to get into Windsor Castle went all the way down St Albans Street next to the castle and up to Park Street, with staff trying to keep everyone entertained in the sunshine.
One local resident told MailOnline that the queue was 'going back almost to the Long Walk' and the number of police officers in the area was 'more than doubled'.
He added: 'Since King Charles and the Princess of Wales had their cancer announcements, Windsor Castle has never been so busy.
'Now the bulk of them seem to be American tourists flocking back over. They're all hoping for a glimpse of King Charles when they go round the grounds.
'This has probably been the record this year and probably since the Queen's death. This is just a regular week, it's nice weather but it's not boiling hot.
'Even in the rain back in March and April they were queuing up for ages under their umbrellas. Today was unusually busy because of the Garter.'
Princess Anne and the Prince of Wales arrive to attend the service at Windsor Castle today
King Charles III and Queen Camilla attend the Order of the Garter service in Windsor today
The Right Honourable Baroness Catherine Ashton arrives to attend the service in Windsor
A view of the procession to attend the annual Order of the Garter service in Windsor today
The Duchess of Gloucester, Princess Royal, the Duke of Edinburgh and the Prince of Wales arrive to attend the annual Order of the Garter Service at St George's Chapel today
King Charles III arrives to attend the annual Order of the Garter Service in Windsor today
A view of the procession to attend the annual Order of the Garter Service in Windsor today
Former prime minister Sir Tony Blair arrives to attend the service at Windsor Castle today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
The Prince of Wales arrives to attend the annual Order of the Garter service in Windsor today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
After the snap General Election was called last month by Prime Minister Rishi Sunak for July 4, Buckingham Palace said the Royal Family would postpone engagements 'which may appear to divert attention or distract from the election campaign'.
However, this was not a blanket ban and visits are being considered on a case-by-case basis – with the Garter Day service among the events given the go-ahead.
Garter Day sees Ladies and Knights of the Order of the Garter - the country's oldest and most senior Order of Chivalry - process down the hill from the Berkshire castle's State Apartments to St George's Chapel.
They are dressed in white plumed hats and dark blue velvet robes, and watched by crowds of onlookers.
The ceremony heralds a busy period for the royals, with the King and Queen expected at Royal Ascot in the coming days, and the following week they will host a state visit by Japan's Emperor.
Hundreds of spectators lined the procession route with many taking hampers and camping chairs to add a summer picnic feel to the occasion.
The palace confirmed in advance that Charles, Camilla and members of the Royal Family would depart by carriage afterwards and return to the castle.
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
A view of the procession to attend the annual Order of the Garter service today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
A view of the procession to attend the annual Order of the Garter service today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
King Charles III arrives to attend the Order of the Garter service at Windsor Castle today
Lord Andrew Lloyd Webber (centre) arrives to attend the Order of the Garter service today
(bottom left to right) The Princess Royal, the Duke of Edinburgh and the Prince of Wales arrive to attend the annual Order of the Garter service at St George's Chapel, Windsor Castle today
Former prime minister Sir John Major arrives to attend the Order of the Garter service today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
Former prime minister Sir Tony Blair arrives to attend the Order of the Garter service today
The installation of new Companions of the Order - including composer Andrew Lloyd-Webber who has been made a Knight Companion - took place during the service.
Theatre impresario Lord Lloyd Webber, whose hit musicals include The Phantom Of The Opera, Cats, Jesus Christ Superstar and Joseph And The Amazing Technicolor Dreamcoat, also attended a private investiture in the castle's Garter Throne Room earlier today.
Also being invested was the Duchess of Gloucester as a Royal Lady of the Garter, as well as Lord Kakkar, emeritus professor of surgery at University College London and Air Chief Marshal the Lord Peach, who have both been made Knight Companions.
The Order of the Garter was established nearly 700 years ago in 1348 by King Edward III who was inspired by tales of King Arthur and the chivalry of the Knights of the Round Table.
A view of the procession to attend the Order of the Garter service at St George's Chapel today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
The Duke of Edinburgh (left) and Prince of Wales arrive to attend the service in Windsor today
A view of the procession to attend the annual Order of the Garter service in Windsor today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
Queen Camilla arrives to attend the annual Order of the Garter service in Windsor today
A view of the procession to attend the annual Order of the Garter Service in Windsor today
Lord Andrew Lloyd Webber arrives to attend the annual Order of the Garter service today
(left to right) The Duke of Edinburgh and the Prince of Wales arrive for the service today
The Duchess of Gloucester arrives to attend the annual Order of the Garter service today
Former prime minister Sir Tony Blair arrives to attend the Order of the Garter service today
(left to right) The Princess Royal, the Duke of Edinburgh and the Prince of Wales arrive today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
The Garter is awarded by the sovereign for outstanding public service and achievement.
Last Thursday, Buckingham Palace announced that Baroness Manningham-Buller, the former director general of MI5, had been named as the Order of the Garter's new Chancellor.
Lady Manningham-Buller, who served for more than 30 years with the intelligence service including five years as its director general, was appointed to the role by the King.
The decision is the King's gift, made without consulting ministers, and from today the peer becomes the first woman to hold the post since the office's inception in 1475, and will succeed the Duke of Abercorn, retiring after 12 years.
Lady Manningham-Buller sits as a crossbench peer in the House of Lords and was appointed a Lady Companion of the Most Noble Order of the Garter by Queen Elizabeth II in 2014, after she retired from MI5 seven years earlier.
Former prime minister Sir Tony Blair (centre) arrives to attend the service in Windsor today
The Prince of Wales arrives to attend the annual Order of the Garter service in Windsor today
The Princess Royal (left), Duke of Edinburgh (centre) and Prince of Wales arrive to attend the annual Order of the Garter Service at St George's Chapel today
(bottom left to right) The Princess Royal, the Duke of Edinburgh and the Prince of Wales arrive to attend the annual Order of the Garter Service at St George's Chapel in Windsor today
Sir Tony Blair arrives to attend the annual Order of the Garter Service at Windsor Castle today
King Charles III and Queen Camilla arrive to attend the Order of the Garter service today
Sir Tony Blair (centre left) arrives to attend the annual Order of the Garter service today
Members of the Household Cavalry Regiment march ahead of the service in Windsor today
The Prince of Wales, the Duchess of Edinburgh, the Duke of Edinburgh and the Princess Royal attend the annual Order of the Garter Service at St George's Chapel, Windsor Castle, Berkshire
Princess Anne and her husband Tim Lawrence ride in a carriage on the day of attending the Order of the Garter service, which is held at St George's Chapel at Windsor Castle, in Windsor, Britain, June 17, 2024
Cherie Blair, the wife of former prime minister Tony Blair, arrives for the service today
Crowds gather ahead of the Order Of The Garter Service at Windsor Castle this afternoon
King Charles smiled at the crowd at the Order of the Garter Service in Windsor today
Crowds gather ahead of the Order Of The Garter Service at Windsor Castle this afternoon
Sophie, Duchess of Edinburgh arrives for the Order of the Garter service in Windsor today
The Household Cavalry Band musicians make their way past the Lower Ward this afternoon
Members of the Household Cavalry Regiment standing to attention ahead of today's service
A view of the procession to attend the Order Of The Garter Service at Windsor Castle in Windsor, England, Monday June 17, 2024. The Order of the Garter is the oldest and most senior Order of Chivalry in Britain, established by King Edward III nearly 700 years ago.
Prince Edward, Duke of Edinburgh and Prince William, Prince of Wales attend the Order Of The Garter Service at Windsor Castle
Heralds including Alastair Bruce of Crionaich attend the annual Order of the Garter Service at St George's Chapel, Windsor Castle, Berkshire
Members of the Household Cavalry Regiment march ahead of the service in Windsor today
Sophie, Duchess of Edinburgh arrives for the Order of the Garter service in Windsor today
Composer Andrew Lloyd Webber attends the Order of the Garter service at Windsor Castle on June 17, 2024
A view of the procession to attend the Order Of The Garter Service at Windsor Castle in Windsor
The Household Cavalry Band musicians make their way past the Lower Ward this afternoon
A woman looks a picture of Windsor Castle ahead of the Order of the Garter Service today
The Royal Standard flies over Windsor Castle ahead of the Order Of The Garter service today
Lord Andrew Lloyd Webber (centre) leaves after attending the annual Order of the Garter Service at St George's Chapel, Windsor Castle, Berkshire
Former British Prime Minister Tony Blair (C) looks on following the Order Of The Garter Service at Windsor Castle on June 17, 2024
The main focus of her work with MI5 was counter-terrorism, both international and domestic, and during her tenure terrorists launched the July 7 bombings in London and terrorism risk assessments were made public.
Charles also appointed Lord Ashton of Hyde, a former Conservative chief whip in the Lords, to the largely ceremonial role of Master of the Horse.
The holder in centuries past was responsible for the sovereign's horses, coaches and travel arrangements and today is titular head of the Royal Mews, which looks after royal vehicles such as state Bentleys and carriages.
Lord Ashton will replace the serving Master of the Horse, Lord de Mauley, whose final major duty was to ride in Trooping the Colour ceremony as holders of the post are present when the Royal Mews supports state occasions.
It comes after Charles's official birthday celebrations on Saturday, where the Princess of Wales made her first public appearance this year.
Prince William, Prince of Wales, Sophie, Duchess of Edinburgh and Prince Edward, Duke Of Edinburgh (R) leave following the Order Of The Garter Service
Prince Richard, Duke of Gloucester and Birgitte, Duchess of Gloucester depart the Order Of The Garter Service at Windsor Castle on June 17, 2024 in Windsor
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
People wait to get into Windsor Castle this morning ahead of the annual Garter Day service
Kate looked relaxed during her first day in the spotlight following her cancer diagnosis for the traditional Trooping the Colour ceremony.
With the King also suffering from cancer, it was a rare joint public outing for the entire family after a period of uncertainty.
Kate rode to the event in a carriage with her children, while William, the Princess Royal and the Duke of Edinburgh were on horseback.
The King also rode in a carriage with the Queen, a departure from last year because of his illness.
Both Kate and Charles have thanked the public for their support after going public with their illnesses, with Kate saying she had been 'blown away' by the 'kind messages' that had made a 'world of difference to William and me and has helped us both through some of the harder times'.
The Prince and Princess of Wales with their children, Prince George, Prince Louis, and Princess Charlotte, on the balcony of Buckingham Palace in London, to view the flypast following the Trooping the Colour ceremony in London on Saturday
The Princess of Wales and Prince Louis arrive for the Trooping the Colour ceremony at Horse Guards Parade in London on Saturday
Prince George, the Prince of Wales, Prince Louis, the Princess of Wales, Princess Charlotte, King Charles III, Queen Camilla, the Duchess of Edinburgh, the Duke of Edinburgh and Lady Louise Windsor on the balcony of Buckingham Palace in London, to view the flypast following the Trooping the Colour ceremony on Saturday
King Charles III arrives for the Trooping the Colour ceremony at Horse Guards Parade in London on Saturday
Kate was initially admitted to hospital for abdominal surgery on January 16 and at the time her condition was thought to be non-cancerous, but cancer was found following the successful operation.
Charles was admitted to hospital just days after Kate, also for a procedure deemed unrelated to cancer.
In February, Buckingham Palace confirmed that he had been diagnosed with a form of cancer, which is not prostate cancer, that was discovered while the King was being treated at the private London Clinic for an enlarged prostate.
Charles initially postponed public-facing duties but resumed at the end of April, speaking of his 'shock' at being diagnosed with cancer as he met patients during a visit to University College Hospital Macmillan Cancer Centre in central London.
