The King led the nation’s Remembrance Sunday commemorations as he laid a wreath at the Cenotaph during a two-minute silence.
Charles, who is still receiving cancer treatment, paid his respects without the Queen, who did not attend events in central London due to a chest infection.
He appeared alongside his son Prince William and daughter-in-law, Kate, Princess of Wales, who carried out two consecutive public engagements for the first time this year after her cancer treatment ended.
Sunday was the King’s third Remembrance service as monarch.
The Royal British Legion’s veteran parade along Whitehall featured 10,000 veterans from 326 different armed forces and civil organisations.
Similar memorial events took place in Edinburgh, Cardiff, and Belfast, as well as smaller towns and cities.
Politicians from the four nations laid wreaths in capital cities, while veterans and their families also gathered for events in Portsmouth, the home of this year’s D-Day anniversary commemorations, and the National Memorial Arboretum in Staffordshire.
Overwhelming sense of family and duty as royals and veterans reunite
As you watch the crowds gathering along Whitehall close to the Cenotaph, the sense of family is overwhelming.
For the military and for the monarchy it is a moment in the year where they all come together.
The Royal Family wouldn’t have wanted us to dwell on their attendance, but in a year when the health of the King and Princess of Wales has cast doubt on what they would or wouldn’t be able to do, the appearance of both was significant.
The presence of the princess was particularly significant, as she gradually returns to work. Before this weekend we were regularly briefed that she would do all she could to be here. Not because she feels she needs to be seen for her sake, but to reflect the focus back onto those who have made the ultimate sacrifice, and to support her family.
With the Queen told to rest at home because of a chest infection, the Prince and Princess of Wales’s joint appearance and support were even more important for the King, who despite continuing his cancer treatment continues to soldier on with his duties.
From watching his mother for so many years and now doing it himself as monarch, he will view placing the wreath at the foot of the Cenotaph on behalf of the nation as one of his most significant responsibilities, one he could not miss.
As ex-servicemen and women paraded past the Cenotaph there was applause. The sombre moment of reflection was replaced by a desire from the crowds to recognise and celebrate their service.
Remembrance Sunday is a day where you watch those who have served together, and shared so much, enjoying each other’s company in happier times.
It’s also a day when the royals reunite, when their personal struggles are inconsequential to them – and their duty comes first as they reaffirm their commitment to the armed forces.
Thousand of people, including Prime Minister Sir Keir Starmer and eight of his predecessors, watched as the nation fell silent at 11am.
Among the former leaders were Rishi Sunak, Liz Truss, Boris Johnson, Theresa May, Lord David Cameron, Gordon Brown, Sir Tony Blair, and Sir John Major.
Kemi Badenoch, the new Conservative Party leader, also laid a wreath alongside the prime minister.
On Saturday evening, the Prince and Princess of Wales attended the Festival of Remembrance at the Royal Albert Hall, along with the King.
Hours beforehand, Buckingham Palace announced Queen Camilla would not be attending either of the Remembrance events. It is understood there is no cause for concern but that doctors did not want to hinder her recovery or put anyone else at risk.
Please use Chrome browser for a more accessible video player
0:44
Princess of Wales at Remembrance Sunday
This year marks the 80th anniversary of the D-Day landings of the Second World War and the 25th anniversary of the end of the war in Kosovo.
It also marks the 75th anniversary of NATO and the 120th anniversary of the Entente Cordiale between the UK and France.