Two family members are poised to run the route their prisoner of war ancestor took as he escaped from a German camp a century ago.

James Dean and his father Paul, 53, from Devon, will retrace the 250km that Second Lieutenant Jock Tullis took after he escaped from the prison in Holzminden on July 23 1918.

James said they were aiming to replicate the path his great-grandfather took 100 years ago as closely as possible as they head from the German town to Losser, on the Dutch border.

“When we found his memoirs, although it doesn’t give the exact route, it gives us a rough route and I think that is what really sprung the idea in dad’s head,” the 19-year-old said.

“It started out as a suggestion … then we talked about it again and we both decided we would like to do something like this. We knew physically we could do it.”

James said his great-grandfather, who was in the Royal Flying Corps, spent two years as a prisoner of war after he had to land his two-seater Sopwith behind enemy lines.

Second Lt Tullis had been on a reconnaissance mission around 80 miles from the border when disaster struck and he was captured.

“While he was flying, his observer was shot in the jaw, and his own gun jammed and they started making their way back and then the engine failed,” James said.

“He had no option but to land, but it was seen by hordes of Germans, and he had absolutely no chance.”

Eventually ending up at the camp in Holzminden, imprisoned along with more than 550 other officers, the inmates spent nine months constructing a tunnel to escape.

James said 86 were on the list to break out during the first attempt but that the 30th man got stuck, bringing the escape to an end.

His great-grandfather made it out as one of the lucky 29, and spent two months with two other individuals trying to make it to safety without getting caught.

James, who will begin a neuroscience degree at Bristol University in September, said: “He was out there quite a while – 250km for us just running it straight – we can do it in a week.

“But when you know you have got to keep moving because you have got the guards from the camp behind you, and avoid every other German out there … it must have been a really, really scary time.”

He said his great-grandfather arrived back in the UK and received a signed letter from King George V which thanked him for his service and welcomed him home.

Second Lt Tullis also returned to discover he was now an officer in the newly formed Royal Air Force – with his commission note stating this happened on April 1 1918, the day the world’s first independent air force was created.

Set to begin their feat on Monday with a short 6km run at just after midnight, the time his great-grandfather escaped, James said he was “excited but full of anticipation”.

“Obviously it is a long way, and while we have been running for as long as I can remember this is the biggest running feat I have taken on before,” he said.

“It is going to be quite a challenge and it is all for a good cause.”

The father and son duo are using the challenge to not only commemorate their family member, but also to raise funds for the Royal Air Force Benevolent Fund.

James said they would also be uploading the memoirs written by Jock onto a blog, along with their own modern day versions as they complete the journey.

“It is amazing to do any sort of charity run, but to have a story behind it and context that people can read I think people will enjoy that,” he added.

To make a donation visit www.justgiving.com/fundraising/rge-100yrs.