An army captain’s dilemma over whether to condemn a comrade to death on the First World War battlefields has been told publicly for the first time.

Captain Francis Hislop and his sergeant discovered a colleague asleep while on sentry duty early one morning in the trenches of northern France.

But rather than turn in the private, to die at the hands of a firing squad, the officer decided to give him a chance.

Now the story has been put in print by the 14-year-old great granddaughter of Captain Hislop, Erin Spivey, for a school project.

The details were related to her by the officer’s son – her granddad – Jens Hislop, a retired police officer who lives at Haworth.

“The story was told to me by my late father some 50 or 60 years ago but until now has never been written down,” he said.

“I am very proud of what my father did in saving a colleague’s life, although others there at the time might have condemned the private to a court martial and firing squad for dereliction of duty.

“Some might criticise my father for his decision but I feel he was right in what he did and I’m very proud of his war service.”

During the war Captain Hislop, a member of the 5th Royal Scots, served at Gallipoli and in northern France.

After the conflict, he went into teaching and then the colonial service. He died in 1966.

Erin – who as part of her project also took in to school her great grandfather’s medals and epaulette – wrote that Captain Hislop and Sergeant Moncur were patrolling the trenches together at 3am one day in 1916 when they came across Private Donaldson asleep at his post.

Relating her great granddad’s story, she said: “I, being the officer, realised that this was a capital offence because the safety of the whole company depended on Donaldson should any enemy appear.

“I was horrified at my situation – that I could be condemning one of my own men to death by firing squad.”

After discussing the situation with his sergeant, Captain Hislop decided to move 40 yards away up the trench and instructed Sgt Moncur to wake the private and give him “the biggest telling off he’s ever had in his life”, and to warn him that the captain was on his rounds.

A few moments later the officer approached.

“Donaldson stood to attention and saluted me and I returned his salute,” he said.

“I asked him if everything was all right and whether his relief was organised. He replied ‘yes, sir’. I smiled at him, saying ‘carry on and goodnight’.

“We exchanged salutes and I continued my patrol.”

Captain Hislop added: “Although I realise my duty to the army was to expose the man and thus condemn him to death, I felt my duty to humanity, my country and his family was much greater.

“You could say I saved his life by not fulfilling my duty as an officer.”