A Field of Remembrance has been set up at Westminster Abbey
Members of the Royal Family have honoured servicemen and women killed in past and current conflicts at the Royal Festival of Remembrance.
The Queen, accompanied by the Duke of Edinburgh, and Prime Minister Gordon Brown joined veterans at the event at London's Royal Albert Hall.
Welsh soprano Katherine Jenkins and tenor Russell Watson performed.
This year marks the 90th anniversary of the end of World War I and several events are planned across the country.
The royal party also included the Prince of Wales and the Duchess of Cornwall, the Duke of York, the Earl and Countess of Wessex, the Princess Royal, Vice Admiral Timothy Laurence and the Duke and Duchess of Gloucester.
WORLD WAR I
Began in 1914 and ended in 1918
One in three UK families had a loved one killed, wounded or taken prisoner
France lost nearly 1.5 million men - double that of Britain
Nearly two million Germans and a similar number of Russians also died
The Massed Bands of the Household Division, the Band of HM Royal Marines, the Band of the Parachute Regiment, the RAF Squadronaires and the Queen's Colour Squadron of the Royal Air Force played.
The festival also included the traditional two-minute silence as thousands of poppy petals fell from the roof of the Royal Albert Hall, each representing a life lost in war.
Territorial Army veterans featured prominently in the event too, as 2008 is the TA's centenary.
A spokesman for organisers, the Royal British Legion, said: "This annual festival commemorates and honours all those who have lost their lives in conflicts and is both a moving and enjoyable evening."
The festival, which included songs and prayers, is being broadcast on BBC One on the eve of Remembrance Sunday, when more than 8,000 veterans will march to the Cenotaph in London's Whitehall.
This year the march will include ex-servicemen and women from Northern Ireland for the first time.
The Somme Heritage Centre in Newtownards, County Down, is hosting a weekend of activities to highlight the role in the allied victory played by more than 200,000 Irish soldiers.
The centre's director, Carol Walker, said for a long time the people of Northern Ireland and the Irish Republic had had differing attitudes towards remembering the war.
"Certainly in the south of Ireland for a long time it was memories that were put away - maybe hidden in a shoebox and put under the bed or up in the roof space.
"But differently in the north, particularly amongst the Protestant community, it would've been remembered more."
This was now changing, she added.