It was the first time their relatives had been allowed to hold a remembrance ceremony at the Whitehall memorial.

About 100 people, including supporters of the War Pardons Campaign, paid tribute to the 306 British and Commonwealth servicemen shot during the war.

Emily Reuben: 75 years for the families to learn that their relatives were not cowards

The Last Post was sounded on the striking of 11 o'clock, before families of the dead quietly laid wreathes at the foot of the Cenotaph.

Many had only recently learnt of the true circumstances surrounding their experiences on the battlefields.

The niece of one of the deserters - William Nelson - saluted as she laid a wreath.

He had heard while in the trenches that his mother had died and that his young sister and brother had no-one to care for them.

At the striking of 11 the Last Post was sounded

Mr Nelson tried to leave the trenches as soon as he could to go and look after them. He was immediately punished for this, and later executed.

Stafford-based Tom Stones's great uncle was shot after being court martialed for allegedly casting away his weapon in the face of the enemy.

He said at the ceremony: "The shameful facts surrounding their deaths were locked away for 75 years in the War Office and we knew nothing about the circumstances surrounding their deaths."

He said the families had so far come halfway in their campaign for the executed to be remembered.

Tom Stones on his great uncle William, who was shot for cowardice

"There's recognition for the first time of the existence of these men but we want pardons for them."

The ceremony in London has reopened the controversy over the government's decision in July not to offer posthumous pardons to soldiers who were shot for cowardice.

The government expressed "regret" about the way they were treated and said the evidence supporting pardons "just does not exist".

Deserters were killed by their own firing squads

Labour MP for Thurrock Andrew Mackinlay is a strong supporter of the campaign to win posthumous pardons for the soldiers - many of whom are now thought ot have suffered post-traumatic stress disorder after enduring months of heavy bombardment in the trenches.

He said after the ceremony: "I think the public interest in this event shows the fact that the issue of gaining pardons for soldiers killed in this way is a massive issue. The government needs to look at it very closely."

The tribute took place ahead of the main Remembrance Day ceremony on Sunday, when the Royal Family, politicians and war veterans will lead Britain in remembering the nation's wartime dead.

Later on Saturday all 160 surviving British veterans who fought on French soil during the 1914-18 war received France's top medal, the Legion D'Honneur.

A party of 13 former soldiers accepted their medals from French ambassador Daniel Bernard at the Imperial War Museum.

Poppies fall on an afternoon remembrance service at the Royal Albert Hall

The men, seven of whom were aged 100 or more, were surrounded by guns, tanks and bomber planes for the moving ceremony.

Robert Burns, who will celebrate his 103rd birthday on Thursday, said: "This is the proudest moment for me since I left the Army.

"It has been wonderful to receive such a permanent memento, but many of the men have been moved to tears."

This evening the Queen and the Duke of Edinburgh will attend the annual Royal British Legion Festival of Remembrance at the Royal Albert Hall, where veterans from the three armed forces will parade in the arena.