King Charles laid the first wreath as thousands gathered in central London to pay tribute to the war dead on Remembrance Sunday.
Prince William and Princess Kate also took part, with the latter making consecutive public appearances for the first time since last December.
Thousands of people lined both sides of Whitehall, with many wearing poppies on a cool, overcast morning in Westminster.
The solemn ceremony followed a two-minute silence observed in the heart of Whitehall and at war memorials in villages, towns and cities across the country.
Kate joined Charles and the Prince of Wales at the Royal British Legion's Festival of Remembrance at the Royal Albert Hall on Saturday evening but the Queen missed the event as she is recovering from a chest infection.
Kate stood throughout the ceremony, watching intently as Charles and her husband, William, placed their poppy wreaths at the base of the Portland stone monument. At the start, she chatted and shared a smile with Sophie, who later placed a gloved hand on Kate’s back in a comforting gesture as they stepped away from the balcony.
Kate joined in singing the national anthem and sang a hymn alongside the Duchess, holding their song sheets.
Among the crowds lining Whitehall were military veterans proudly wearing their medals, while others waited nearby to take part in the Royal British Legion march past the memorial.
A volley from a gun fired by the King's Troop Royal Horse Artillery from nearby Horse Guards Parade rang out to signal the start of the two minutes of silent reflection, punctuated by the sound of London traffic, and another booming blast marked its end.
The King laid his wreath on behalf of the nation, after buglers from the Royal Marines played the Last Post. Charles was followed in doing so by the Prince of Wales, the Duke of Edinburgh, the Princess Royal, with the Queen's equerry Major Ollie Plunket laying her wreath.
Charles wore military dress, as did the other royals, and after laying his wreath he saluted in his greatcoat worn over his uniform of an Admiral of the fleet, with a sword by his side.
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His wreath closely resembled a floral tribute produced for his grandfather King George VI - 41 open-style poppy petals made from bonded fabric mounted on black leaves, traditional for a sovereign's wreath and featuring a tied ribbon in the colours of the King's racing silk - scarlet, purple and gold.
Prime minister Sir Keir Starmer stepped forward to pay tribute to the fallen on behalf of the Government with his floral tribute, as did the Conservative Party's new leader Kemi Badenoch, other party leaders, senior members of the Cabinet, military chiefs of staff and high commissioners.
Standing close to the Cenotaph were an unprecedented eight former prime ministers: Sir John Major, Sir Tony Blair, Gordon Brown, Lord Cameron, Baroness May, Boris Johnson, Liz Truss and Rishi Sunak.
Watching from the Foreign, Commonwealth & Development Office building were Kate standing with the Duchess of Edinburgh, in a neighbouring balcony was Vice Admiral Sir Tim Laurence with the Duke of Kent, and the Duke and Duchess of Gloucester stood together in another.
A military band is also performing as it marches at the Parliament Square end of the central London street.
The Royal British Legion’s veteran parade will see 10,000 veterans, representing 326 different armed forces and civilian organisations, march past the Cenotaph.
This year marks the 80th anniversary of the D-Day landings in 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.
More than 800 sailors, soldiers and aviators were duty on Remembrance Sunday, representing their services at the Cenotaph and at commemorative services at Westminster Abbey and Westminster Cathedral.
The Lord Mayor of Westminster, Cllr Robert Rigby, was at Westminster Abbey to pay respects to veterans and victims of war.
He said: “It is my great privilege to represent the people of Westminster at the traditional Remembrance Service at Westminster Abbey on Sunday.
“Across the week leading up to Remembrance Sunday I have attended a number of events, from Covent Garden to railway stations to Lancaster Gate, and I was moved on each occasion by the feeling of everyone there.
“From a 96-year-old veteran to young cadets, there is a shared sense of thanks and obligation to those who gave their lives in past conflicts to preserve our freedoms.”
