The bells of Big Ben rang 11 times on Sunday to mark the start of a two-minute silence honouring the nation’s fallen soldiers.
Remembrance Sunday is held every year in the UK on the closest Sunday to Armistice Day, which this year fell on 11 November.
This is the first year that King Charles III has led a Remembrance Sunday service as monarch.
He led the UK’s royals and senior politicians in a ceremony at the Cenotaph, the national war memorial in central London, where they laid wreaths in tribute to fallen servicemen and women.
The day’s events also featured a solemn march through the capital, in which 10,000 veterans – from the oldest 100-year-old World War II veterans to the youngest who served in recent conflicts like Afghanistan – took part.
Traditionally, Britons mark the occasion by wearing poppies and observing a national two-minute silence at 11 am.
First Remembrance Day since the Queen's death
This year's ceremony is especially poignant for Britain's royal family because it marks the first Remembrance Day since the death of Queen Elizabeth II, who considered the day one of the most important engagements in her royal calendar.
Elizabeth, who died on September 8 at 96 years old, lived through World War II and only missed seven Cenotaph services during her 70-year reign.
Officials said this year's service is dedicated both to fallen soldiers in wars past and to Ukrainians fighting against Russia's invasion.
“We must never forget those who gave their lives in defence of our values and our great nation," Defence Secretary Ben Wallace said.
“All of us will also be thinking of those brave Ukrainians who are fighting for their very own survival to defend freedom and democracy for all, just as the UK and Commonwealth soldiers did in both world wars."
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