In the centenary year of the outbreak of World War One, much of the debate and discussion has focused on whether Britain should have gone to war – and the millions of lives that were lost across Europe.

But it has also thrown a spotlight on the thousands of British men who refused to fight.

An estimated 16,000 conscientious objectors (COs) rejected the call-up after conscription was introduced in March 1916, whether on the grounds of religious faith or their moral or political convictions.

Many were from the pacifist Quaker movement, some were committed socialists who saw it as an unjust and imperialist war, others were simply determined not to play any part in organised killing.

In contrast with how they have been viewed by some, the thousands were remembered as courageous men at a stirring memorial ceremony in Camden, held on International Conscientious Objectors’ Day on May 15.

Many faced incredible hardships, enduring repeated imprisonment in appalling conditions with back-breaking labour. Some were sentenced to death, although their sentences were commuted, while 73 men lost their lives as a result of their dire treatment.

The ceremony was held at Tavistock Square by a granite memorial, which was erected in the Bloomsbury square in 1994.

Hundreds of people gathered at the ceremony, including the relatives of 50 objectors.

Among them was Paul Silverman, whose father Sydney, the Labour MP, was court-martialed and sentenced to two years’ hard labour.

Sydney, who lived for 20 years in Finchley Road, Hampstead, would go on to serve in the House of Commons from 1935 until his death in 1968.

He was best known for his private members’ bill which abolished capital punishment for murderers in 1965.

Mr Silverman, 80, of Cheverton Road, Archway, said: “He was very much opposed to the war on political grounds as a socialist.

“His opposition to the death penalty and his conscientious objection were linked, because of his antagonism to the death penalty. One led to the other.”

He added that his father took a different position towards the Second World War, being a leading Jewish figure who was one of the first people to hear about the atrocities of the Holocaust.

“He was not against struggle,” he said.

“What he was against was militarism and armies, and the fact that the aim of war is to inflict capital punishment on the enemy, on enemy soldiers.”

The International Conscientious Objectors Day featured performances from the gospel choir of Maria Fidelis Catholic School in Somers Town.

Family members carried photos of their relatives and laid flowers at the granite memorial.

They included Jeremy Attlee, grandson of architect Tom Attlee, whose brother Clement enlisted during the war before going on to become Prime Minister in 1945.

The Christian pacifist was an “absolutist” – an objector who also refused non-combatant service such as ambulance or farm work – and was jailed for more than two years.

Mr Attlee, 71, of Upper Park Road, Belsize Park, said: “I’m proud of what he stood for and in agreement with what he stood for.

“It was a terrible time for everybody with very difficult decisions to make.

“I respect those who took different decisions, but I think he made the right decision and history has proved him right. It was a pointless war which cost millions of lives and caused untold suffering.”

Simon Colbeck, 59, a social worker and Quaker from Watford, spoke about his grandfather’s cousin, Catherine Marshall, one of the few women to be honoured at the event.

Catherine, who lived in Linnell Drive, Golders Green, was a prominent activist and a significant figure in the campaign against conscription, and instrumental in persuading Britain’s greatest philosopher, Bertrand Russell, to take up the cause.

Mr Colbeck said: “There’s still a tendency to think they were just cowards, using it as an excuse.

“It’s important to remember how some died in prison and some were prepared to face the firing squad for their beliefs.”