One of the cast members of upcoming war epic 1917 made a personal discovery while preparing to make the film.

The acclaimed new Sam Mendes film follows two young British soldiers at the height of World War I in Spring 1917 as they are charged with delivering a warning to their comrades heading into a German trap on the Hindenburg Line.

The story is based on a tale the director heard from his grandfather and veteran Alfred Mendes.

But the director wasn't the only person working on the film who had a familial connection to the war.

Speaking at a press conference today (December 5) to Mirror Online and other publications, Game of Thrones actor Dean-Charles Chapman - who played King Tommen Baratheon in the hit fantasy saga - discussed his own research into World War One as he prepared to play Lance Corporal Blake.

British actor Dean-Charles Chapman poses on the red carpet as he arrives to attend the World premiere and Royal Film Performance of the film "1917" in London on December 4, 2019, in support of the film and TV charity (
Image:
AFP via Getty Images)

Chapman revealed: "I read a book called The Western Front Diaries and it's snippets of diary entries from the soldiers in the First World War. I actually found my great-great grandfather actually had a diary entry in that book.

"He talks about how he fought in the First World War - he was part of a cavalry - he got shot, was wounded in No Man's Land and survived out there for four days."

The British actor also spoke about his grandfather's life after the horrors of the Great War ended at the conference which was also attended by star George MacKay and supporting players Mark Strong , Andrew Scott , and Claire Duburcq.

Dean-Charles Chapman in 1917 (
Image:
Universal Pictures)

"He actually survived the First World War and ended up working in the first poppy factory that opened in Richmond in London," detailed Chapman. "So, I read that to get in the head-space for stepping onto set."

The incredible story speaks volumes as to what real-life soldiers had to endure if they had hope of survival on the Western Front, which is no doubt translated in Mendes' epic film.

The film also stars Richard Madden , Colin Firth , and Benedict Cumberbatch .

1917 is released in UK cinemas on January 10, 2020.

Will you be seeing 1917 in cinemas? Let us know in the comments below.