Siegfried Sassoon received the Military Cross for his bravery on the Western Front, but for years it was believed he had thrown the medal into a river.
He was a decorated hero whose poems on the brutality of the First World War stirred the emotions of a nation.
Siegfried Sassoon received the Military Cross for his bravery on the Western Front, but for years it was believed he had thrown the medal into a river in protest.
Now, 90 years later, the medal has been found in a treasure chest in the attic of a family house on Mull.
It is being put up for auction and it is expected that the medal, together with Sassoon's identification tag, will fetch up to £25,000 at Christie's in London.
A Webley revolver also found in the loft has been donated to the Imperial War Museum.
Robert Pulvertaft, 45, whose stepfather George was Sassoon's only son, is selling the medal on behalf of the family.
"Like most people, I thought it had been thrown into the Mersey," he said. "I found it while clearing out the attic of the family property on Mull. It was in a treasure chest, like a pirate's chest, covered in cobwebs and long-dead insects.
"The ID tag was there too, with the revolver in an old padded bag and some poetry medals."
Sassoon, best remembered for Memoirs of a Fox Hunting Man, was born in Kent in 1886. In 1915, he was commissioned into the Royal Welch Fusiliers and sent to France. He was nicknamed "Mad Jack" for his at times near-suicidal exploits in the trenches.
He was awarded the MC after remaining for 90 minutes under heavy fire collecting and bringing back British wounded and dying during a raid on enemy trenches, on May 26, 1916.
In April 1917 he was wounded and returned to England, where he met prominent pacifists and his disillusionment with the war grew. In June 1917 he sent a letter to a national newspaper claiming that the war was being deliberately prolonged by the government. He refused to return to duty.
It was that year that Sassoon was thought to have thrown his MC away - but it was only the ribbon. In Memoirs of an Infantry Officer, published in 1930, he wrote that while walking along the dunes he shook his fists at the sky in "a paroxysm of exasperation". He added: "Feeling no better for that, I ripped the MC ribbon off my tunic and threw it into the mouth of the Mersey."
Sassoon was threatened with a court martial, but his friend and fellow poet Robert Graves convinced officials that he was suffering from shell shock.
He was sent for treatment to the Craiglockhart War Hospital for Officers, in Edinburgh, now part of Napier University, where he struck up a friendship with fellow poet Wilfred Owen.
Their encounter provided the subject for Pat Barker's novel Regeneration and the 1997 film of the same name.
Sassoon had several homosexual relationships but later married Hester Gatty and had a son, George. George's fourth wife was Alison Pulvertaft, with whom he sometimes stayed in Wiltshire and on Mull, where he left his MC in the attic.
Sassoon died in 1967 aged 80.
Also included in the Christie's auction, on June 6, is Sassoon's first edition copy of Robert Graves's Goodbye To All That, embellished throughout with Sassoon's comments, which could fetch up to £12,000.
Thomas Venning, of Christie's, said: "The medal reminds us first of all of the First World War in all its misery. It is unusual to have a single object that has the ability to sum up a whole period in this way."
