A teacher spotted her own granddad in a school book about World War One.
The picture was taken in Ypres, Belgium in 1917 and shows William Ensor carrying an injured soldier on a stretcher through a muddy battlefield during the Battle of Passchendaele.
Kathryn Robyns spotted the photo of William, who was a stretcher bearer in the army, while working at Ysgol Uwchradd Bodedern school in her hometown.
Kathryn, of Anglesey, North Wales, said: 'I realised immediately that my grandfather was in the picture.
'He always said that he didn't want to go to war to kill and the best way he could help the cause was to go as a stretcher bearer.'
Mr Ensor did not talk about his service but he featured in photos which became iconic among war records.
The Battle of Passchendael, officially known as the Third Battle of Ypres, Passchendaele - became famous for the scale of casualties and the amount of mud on the battlefield.
The photo was taken on 1 August 1917 by Lt John Warwick Brooke - an official photographer for the British Army.
The photograph has since been digitally coloured by the Imperial War Museums.
Kathryn, who is now retired, said her grandfather, also from Anglesey, was sent to the Western Front after completing basic first aid.
She said: 'My grandfather was a hero to us - not because of his service but because he was extraordinarily kind.
'He never talked much about the war, but I do remember that every year on Armistice Day, he would crave company and I'd sit with him then many times.
'The one thing he would say that hit him most was losing friends.'
Mr Ensor, who enlisted in the army in 1915, survived the war and worked as a surveyor. He died at the age of 83 in 1969.
Kathryn said: 'He was a very special man and it was very moving to spot him..'