The Queen led the Remembrance Sunday ceremony in central London today, as tributes took place across the country to remember Britain's war dead.
Services also took place in Iraq and at Kandahar, the UK's largest military base in Afghanistan.
This year's events fall just two days before the 90th anniversary of the armistice, the end of the first world war.
The Queen was joined by the prime minister, opposition party leaders, the foreign secretary, David Miliband, and hundreds of veterans during the wreath-laying ceremony at the Cenotaph.
Veterans, many elderly and frail, assembled on Horse Guards Parade and march to the Cenotaph, to stand on the north side of the square.
The Queen stood solemnly at 11am to mark the two-minute silence and then approached the Cenotaph to lay a wreath, pausing for a moment's reflection, before rejoining her family.
The Duke of Edinburgh, Prince Charles and Prince William - an officer in the Blues and Royals - followed in making the gesture, each saluting as they did so. Gordon Brown followed with the first of the wreaths to be laid by the leaders of the UK's main political parties.
A frail-looking Baroness Thatcher, 83, was accompanied by former Tory prime minister John Major throughout the service.
Stuart Gendall, spokesman for the Royal British Legion, said: "It is the 90th anniversary of the end of world war one, supposedly the war to end all wars, and yet here we are today and conflicts are still ongoing.
"One-hundred-and-twenty-one young men and women have lost their lives in Afghanistan."
He said that it was important for the nation to come together and remember all those that laid down their lives fighting for their country.
The service honoured those who served in the first and second world wars as well as those who died in more recent conflicts in Iraq and Afghanistan.
Commemorative events were being held this year for both the 15-year deployment in Bosnia and Herzegovina, and the 38 years in Northern Ireland under Operation Banner.
For the first time, the Territorial Army - which is celebrating its 100th anniversary - was granted the privilege of also laying a wreath at the monument.
The Prince of Wales, a colonel in the Welsh Guards, took part in the Welsh Guards' remembrance service at the Guards' Chapel in central London. He laid a wreath at the Guards' Memorial and later present medals for long service and good conduct.
Meanwhile, one second world war veteran was attending his first Remembrance Day parade, at the age of 98.
Arthur Hillman has never attended Poppy Day services before today because he refused to see himself as a war hero and preferred to stay at home nursing his wife.
His regiment, the Desert Rats, fought in the battles of El Alamein and Monte Cassino, serving under General Montgomery in the Household Cavalry's Life Guards. But until now Hillman left his medals in their original casing and would not go to war parades.
It was only after the deaths of his late wife and second partner that he joined the British Legion and agreed to commemorate his achievements.
He told the Western Daily Press: "I never did anything heroic like rescuing soldiers or anything like that.
"I'm determined and a very independent person but I'm also quite modest and that's partly the reason why I didn't wear the medals.
"I am looking forward to the parade but I expect it to be emotional."
Last night, the Queen attended a special remembrance service at the Royal Albert Hall.
She was joined by the Duke of Edinburgh, the Prince of Wales, the Duchess of Cornwall, the Duke of York, the Earl and Countess of Wessex and the Princess Royal.
Gordon Brown and his wife Sarah also attended the event, which was organised by the Royal British Legion.
The Royal Festival of Remembrance has been held annually since 1927, and this year featured a prominent role for Territorial army veterans, as it is the TA's centenary year.