Politicians, Royal Family members and veterans are commemorating those who lost their lives in conflict as the UK marks Remembrance Sunday.
At 11:00 GMT, a two-minute silence was held across the country.
Boris Johnson, Jeremy Corbyn and Jo Swinson have broken away from the election campaign to attend the annual ceremony at the Cenotaph in London.
Prince Charles laid a wreath during the service on behalf of the Queen, who was watching from a balcony.
Also in attendance are the Duke and Duchess of Cambridge and the Duke and Duchess of Sussex.
The beginning and end of the two minutes’ silence were marked by the firing of a gun by the King’s Troop Royal Horse Artillery.
The service at the Cenotaph honours the armed forces community, British and Commonwealth veterans, the allies who fought alongside the UK and the civilian servicemen and women involved in the two world wars and later conflicts.
Cabinet ministers, religious leaders and representatives of Commonwealth nations are attending alongside hundreds of members of the armed forces.
The Duke of Cambridge and the Duke of Sussex followed Prince Charles in laying wreaths.
Several former prime ministers including Sir John Major, Tony Blair, Gordon Brown, David Cameron, and Theresa May, are also attending.
After wreaths were laid, Bishop of London Dame Sarah Mullally led a service that was due to end with the Royal Air Force sounding the bugle call, Rouse.
Following the service, up to 10,000 war veterans are marching in a slow procession past the war memorial.
World War Two veteran Ron Freer, 104, who is blind, is thought to be the oldest person marching at the Cenotaph this year.
The Remembrance Sunday commemorations always hold “special significance” for him because his father was killed in 1918 and is buried at Dernancourt Communal Cemetery in the Somme, France, according to Blind Veterans UK.
Speaking ahead of the ceremony, Mr Johnson said he would be “proud” to lay his first wreath at the Cenotaph as prime minister, and vowed to continue to “champion those who serve today with such bravery in our military”.
He said in a tweet he would be “thinking of the men and women who, over the centuries, have given so much to protect our country”.
Labour leader Mr Corbyn said in a video message: “We are all here today because we owe so much to those who came before. And today we remember them.”
Many serving personnel, veterans and their families were “not getting the support they deserve”, he said.
And Liberal Democrat leader Ms Swinson said people should pause to reflect and remember how “fragile” peace can be.
The trio will be joined by the SNP’s Westminster leader Ian Blackford and the DUP’s Nigel Dodds.
Elsewhere, Scotland’s First Minister Nicola Sturgeon laid a wreath at the Stone of Remembrance at Edinburgh City Chambers before giving a reading at the service at St Giles’ Cathedral.
In Northern Ireland, Taoiseach Leo Varadkar is due to attend a Remembrance Sunday service in Enniskillen, County Fermanagh.
Ceremonies are also taking place across Wales, including at the Welsh National War Memorial in Cardiff.
This year marks 100 years since the first two-minute silence was observed to mark Armistice Day on 11 November 1919.
The ceremony at the Cenotaph comes after Prince Harry, Meghan, Prince William and Kate joined the Queen at London’s Royal Albert Hall on Saturday for the Festival of Remembrance.
It was their first appearance as a group since Harry and Meghan said they were struggling with public life.