It was only when he turned 100 that the veteran of Ypres began to speak about the horrors he had seen

It was just 11 years ago, when he turned 100, that Harry Patch first began to talk about his experiences fighting in the first world war.

It was a week ago that he became the last surviving soldier in the country who had seen at first hand the horror of the trenches.

Yesterday, Harry Patch died peacefully in his bed at his residential home in Wells, Somerset, a man who spent his last years urging his friends and many admirers never to forget the 9.7 million young men who perished during the 1914-18 war.

Last night, it was announced that a special commemoration service for the entire generation of British soldiers who died in the first world war will be held at Westminster Abbey, attended by the Queen and military and political dignitaries.

“War isn’t worth one life,” Patch, nicknamed “the last fighting Tommy”, would say. So traumatised was he by his experiences at the 1917 battle of Passchendaele – which claimed the lives of 70,000 men – that each year Patch locked himself away in a private vigil for his fallen friends.

It was seven days ago that Henry Allingham, 113, Britain’s oldest man and a fellow veteran of the trenches, died; with both men has gone Britain’s last living link to one of the most traumatic events in modern history. The prime minister said it was the passing of the “noblest of all the generations”.

“I had the honour of meeting Harry, and I share his family’s grief at the passing of a great man. The noblest of all the generations has left us, but they will never be forgotten,” said Gordon Brown. “We say today with still greater force, ‘We will remember them’.”

Harry Patch was born on 17 June 1898 in Combe Down, near Bath in Somerset. He left school at 15 to learn his trade as a plumber. He turned 18 just as conscription was brought in and, after six months’ training, he was on the frontline with the Duke of Cornwall’s Light Infantry. He was in the trenches at Ypres between June and September 1917, where he and his gang of five machine gunners made a pact not to kill an enemy soldier if they could help it: they would aim for the legs.

In September 1917, a shell exploded above Patch’s head, killing three of his comrades; he was hit by shrapnel in the lower abdomen, but survived. Every year since then Harry would remember that day.

“He would just lock himself away and remember his friends,” said author Max Arthur, whose 2005 book Last Post documented the words from the last 21 survivors of the war. “Last week, there was just one; now there is no one alive who has seen what Harry saw in the trenches. Harry said it was just the most depressing place on earth, hell with a lid on,” he said.

Arthur said the horrors of Passchendaele stayed with Patch throughout his life. Patch exhibited the signs of post-traumatic stress and even opening a fridge and being confronted by its interior light sometimes became a “traumatic experience, the light resembling an explosion”.

After the war, Patch returned to his trade as a plumber and married Ada, whom he had met while convalescing. They were married in 1919 and had two children, Dennis and Roy. His wife died in 1976 and his sons have also since died. Too old to fight in 1939, Patch became a maintenance manager at a US army camp and joined the Auxiliary Fire Service. He retired in 1963 and in 1980 married again, to Jean, only to be widowed a second time five years ago. His third partner, Doris, who lived in the same retirement home, died last year.

It was only on his 100th birthday that Patch came into the spotlight, when for the first time he allowed reporters to visit his care home. His autobiography, The Last Fighting Tommy, written with Richard van Emden, was published in 2007. “He was the last of that generation and the poignancy of that is almost overwhelming,” said van Emden yesterday. “He remembered all of those who died and suffered, and every time he was honoured he knew it was for all of those who fought.”

He said that his conversations with Patch were “a real education”. “He had a sparkle about him, a dry sense of humour. He was one of the most rewarding people to be with.”

As well as launching poppy appeals for the British Legion, Patch became an agony uncle columnist for men’s magazine FHM and he even had a cider named after him.

In 1999, he received the Légion d’honneur medal awarded by the French to 350 surviving veterans of the Western Front, dedicating it to his three fallen friends. He revisited the Ypres battlefield and British and German war cemeteries, placing a wreath on a German grave. Patch fervently believed war was “organised murder”. “It was not worth it,” he said. “It was not worth one, let alone all the millions.”

Prince Charles was among those to pay tribute yesterday. “Harry always cherished the extraordinary camaraderie that the appalling conditions engendered in the battalion and remained loyal to the end.”

Yesterday, the Chief of the General Staff, General Sir Richard Dannatt, said he spoke on behalf of all ranks of the army in expressing sadness at the news.

“He was the last of a generation that in youth was steadfast in its duty in the face of cruel sacrifice and we give thanks for his life – as well as those of his comrades – for upholding the same values and freedom that we continue to cherish and fight for today.”

The funeral is in Wells Cathedral.