For millions of soldiers killed in the First World War, the battlefield was their only resting place, their graves forever unmarked. Now, historian Neil Hanson has traced the lives and deaths of three of these soldiers.

AS soon as it was light, crowds began to form outside Victoria station. Platform Eight had been cordoned off since the night before and at eight o'clock the first troops and ex-servicemen began to assemble. At 9.15am the gun carriage and pall-bearers formed up between Platforms Seven and Eight.

Five minutes later, eight men of the Grenadier Guards entered the carriage and draped the coffin with the Union Flag. Then they placed a steel helmet, side arms and a webbing belt on the lid, and carried it out onto the gun carriage.

Crowds ten and 20 deep lined the route as the coffin, accompanied by the massed bands, made its way to Hyde Park Corner, then to Admiralty Arch and Charing Cross, before turning into Whitehall.

At exactly ten minutes to 11 the carriage drew to a halt in front of the Cenotaph, shrouded in Union Flags. Wearing the uniform of a Field Marshal, King George placed a wreath of bay leaves and red roses on top of the coffin.

As the last echoes of the Last Post faded after the two minutes silence, the gun carriage began to move again, taking the coffin to Westminster Abbey, its final resting place.

It was November 11, 1920. Inside the casket was the Unknown Soldier, an unidentified and unidentifiable body exhumed from the fields of Flanders. He was a symbol of all those who had died in the First World War, and those whose graves would never be known.

Of all the million British dead of the First World War, the Unknown Soldier was the only one ever returned to his native land. About 300,000 had no known grave, lost without trace in the battlefield or whose bodies were mangled beyond identification.

And it was the story of the Unknown Soldier which inspired historian and writer Neil Hanson to research the stories of some of those whose bodies still lie unmarked. Using archive material, diaries and letters, he pieced together the lives of three of these soldiers, one British, one German and one American. All three died on the Somme, within gunshot sound of each other, but they were to follow very different paths to their deaths.

Alec Reader was a clerk with the Post Office until he enlisted in the Civil Service Rifles four months short of his 18th birthday. Paul Hub was working as a clerk in Stuttgart when he enlisted in the 247th Infantry Regiment on the outbreak of war. George Siebold had been working in real estate when he volunteered for the Aviation Section of the Signals Corps.

"One thing that always intrigued me was the burial of the Unknown Soldier," says Neil, former landlord of the Tan Hill Inn in Arkengarthdale, on the border of North Yorkshire and County Durham, before he turned to writing. "He became a symbol of the missing fathers and sons and husbands.

"But you bandy these numbers around and it doesn't really mean anything unless you bring it down to a personal level. Each of them is a personal tragedy, a wife robbed of her husband, children robbed of their father.

Alec Reader was under age when he joined up, but as the horrors of the war started to filter back home, there were moves to bring these boy soldiers home. Eventually, Parliament passed a law requiring them to be offered the chance to either come home or leave the front line.

But Alec was unwilling to abandon his colleagues and remained at the front line. His father Fred launched a campaign to have him transferred behind the lines, and eventually Alec agreed. But the paperwork for the transfer took some time to arrive at Alec's unit and when it did arrive the clerk had sent the wrong form. While he was waiting for the right form, Alec was sent over the top at High Wood on the Somme and was killed.

Paul Hub had joined up at the start of the war, much to the consternation of his fiance, Maria Thumm. In his letters home, Paul told Maria he didn't think it would be fair to marry her when it was likely he would leave her a widow, but eventually, after four years of war, he relented.

On June 11, 1918, Paul and Maria married at Stetten. A week later, Paul returned to the front and just ten weeks after his wedding, he was killed at Maricourt, near Amiens. His wife never remarried.

The same day Paul was killed, August 26, 1918, George Siebold took off in his Camel and set course for Baupame, where fierce ground fighting was taking place. But as the pilots of the 148th squadron began their bombing attacks, they were ambushed by a flight of Fokkers.

Hermann Frommherz, a German ace who was to end the war with 32 victories, came out of the sun, taking George unawares. Within seconds the Camel had been hit and was spinning towards the ground.

"These were stories that moved me greatly, but every single story from the First World War is a tragedy and a moving story," says Neil. "In celebrating these three individuals in particular I'm commemorating all those men who fought and died, and fought and lived, in the Great War."

As part of his research, Neil also tracked down surviving relatives of the three servicemen, through census records, other public documents, and, in the case of Paul Hub's family, newspaper advertisements. And this provided some poignant moments.

To the family of George Siebold, he was able to show film he had found in the archives of the University of Texas, giving George's nieces and nephews the chance to see a moving image of their uncle for the first time.

"That was the most moving part of all, and without exception they proved they're still keeping the memory of these men alive," Neil says. "But to me, the unknown soldiers are not just those who don't have a grave, but even those whose fate we know, or those who survived. Their stories should be kept alive."

* The Unknown Soldier by Neil Hanson (Doubleday, £20)