A British PoW captured by the Germans in World War I was freed to see his dying mother - but went back to the prison camp after giving the Kaiser 'his word' he would return.
Capt Robert Campbell, aged 29, was gravely injured and captured just weeks after Britain declared war on Germany in July, 1914.
But after two years in Magdeburg Prisoner of War Camp, the British officer received word from home his mother Louise Campbell was close to death.
He speculatively wrote to Kaiser Wilhelm II, begging to be allowed home to visit his mother one final time.
Incredibly the German leader granted the request allowing the professional office two weeks leave - as long as he returned.
The only bond he placed on the leave was Capt Campbell's 'word' as an army officer.
He returned to his family home in Gravesend Kent in December 1916 and spent a week with his cancer-stricken mother.
He then kept his promise by returning to his German prison - where he stayed until the war ended in 1918.
The remarkable example of wartime honesty was uncovered by historian Richard Van Emden, 48, as he researched his new book.
The author admitted the act of chivalry was rare even for the bygone age of the Great War.
He said: 'Capt Campbell was an officer and he made a promise on his honour to go back. Had he not turned up there would not have been any retribution on any other prisoners.
'What I think is more amazing is that the British Army let him go back to Germany. The British could have said to him 'you're not going back, you're going to stay here'.
'This was totally unique. I think it is such a unique example that I don't think you can draw any parallels.'
Capt Campbell had been leading the 1st Bn East Surrey Regiment when his battalion took up a position on the Monds-Conde canal in north-western France.
But a week later his troops were attacked by the German forces and Capt Campbell was gravely injured and captured by enemy soldiers.
The wounded Brit was treated in a military hospital in Cologne, Germany, before being transported to the Magdeburg Prisoner of War Camp.
In 1916 he was allowed two weeks compassionate leave by the German Kaiser, to include two days travelling in each direction by boat and train.
Capt Campbell reached his mother's bedside on December 7 and spent a week with her before returning to Germany. She finally passed away in February.
The British officer, who had served in the Army for 11 years before the outbreak of war, remained in Magdeburg until the armistice in 1918.
Mr Van Emden discovered the incredible story in correspondence between the British Foreign Office and their German counterparts.
The records also show the Germans contacted the British requesting German national Peter Gastreich be allowed to leave the Isle of Wight to visit his dying father - but the British authorities refused the request.
At the end of the war Capt Campbell was freed from the camp and allowed to make the journey back to the British coast - retiring from the military in 1925.
And despite his traumatising ordeal Capt Campbell was again thrust into military action in 1939 when he rejoined the 1st Bn East Surrey Regiment for the Second World War.
His role as the Chief Observer of the Royal Observer Corps in the Isle of Wight was less precarious than that thirty years earlier.
He managed to survive the war unscathed and died back in his home country in July 1966 aged 81.
Capt Campbell's story has been told in Mr Van Emden's new book, 'Meeting the Enemy: The Human Face of the Great War'.