"The Devonshire’s held this trench, the Devonshire’s hold it still” announces the memorial cross at the entrance to a small First World War cemetery in northern France, where 160 men were killed on the first day of the battle of the Somme.

And it was here that Thomas Dennis’s research brought him while retracing the fabricated footsteps of Albert, the lead in War Horse whom he plays so convincingly.

However, it wasn’t until Thomas came across the grave of a Private Taylor, that he began to wonder about his own fate in Flanders, had he been a young man in 1916.

“It was a very poignant moment for me, because Private Taylor is Albert’s best friend in the play,” Thomas tells me.

Instead, Thomas reimagines the possibilities every night on stage in War Horse, which arrives for its much heralded Christmas run in Oxford next week.

“It just brings it home how real this story was,” he adds.

But it is his love of history, which Thomas believes helped him win the lead role in one of the most famous and successful plays in the West End of all time.

“Albert may not have been a real person but he represents so many men who went to fight in World War One, and War Horse brings all that to life.

“It’s that human element that makes it so emotional, and the need to remember the extent of the devastation.”

Now it’s our turn to enjoy Michael Morpurgo’s rich, evocative storytelling as Thomas takes us from Dartmoor’s farms to the trenches, where he finds his horse Joey.

And as the pair experience the horrors of The Great War, the audience is immersed in their tragic experiences with them.

“War Horse is fundamentally a love story between a boy and his horse, which is then torn apart by this huge conflict, so it’s very humbling seeing how people react,” Thomas adds.

“But as its author Michael Morpurgo says, it is not a play about war, but a play about peace, because no one could come away from watching this, thinking that war is a good thing.”

And what of the puppeteers who bring the horse to life?

“They take the audience on this journey with them and there is a moment right at the beginning, when I look into Joey’s eyes, and he looks back at me, and he’s real from the word go.

“The puppetry is done brilliantly, because the horses aren’t patronised. They can cause damage. And Joey does get sacred and angry. So those around the horses have to react in the right way, for this to work.

“And the audience takes a massive leap of faith with them, which is why the play works so well, because they are committed, they have bought into it.”

As for Albert himself, “he really goes through the darkness, from the thrill of raising Joey through the stress, hope and horror of their journey, so every show is an emotional rollercoaster for me.

“But it’s also a children’s novel which doesn’t shy away from the truth, and what actually happened, while building up to the joy of the reunion at the end.

“It reminds people that the things that are worth fighting for can be a struggle, and without the darkness the play just wouldn’t be as powerful.”

Even so, rather a stark message at Christmas? “Everyone remembers that famous truce on Christmas Day in 1914 when both sides got out of the trenches and met in No Mans Land to exchange gifts and play football, so I think actually the show’s messages are more relevant at Christmas than at any other time.

“It makes everything more meaningful.”

For Thomas though it’s a big part, but having landed another mammoth lead recently, playing Christopher in Mark Haddon’s The Curious Incident of the Dog in the Night-Time, he is well versed in learning realms of lines and staying in the moment on stage.

“Curious Incident was such a physical show that by the end you were on such a high. It was such a buzz. I asked to audition for it for two years, and when they finally acquiesced I got the part luckily,” he grins.

From the frying pan into the fire then, with hundreds of performance scheduled into this current and extensive tour of War Horse?

“I just immerse myself in it every night. It’s a mammoth show so you can’t think about the end, but just live through it moment by moment.

“Because it’s a privilege for an actor to have that much to get your teeth into. Parts like this are the real reason we become actors, to put yourself in someone else’s shoes in front of an audience.

“But when to work with such a beautiful story makes your job so much easier, because it just flows so well and you can focus instead on telling the story.

“So I give it everything I have, because each night is the chance to bring the story alive and it’s such a special show.”

War Horse opens in Wednesday December 13 until Saturday Jan 6. 0844 8713020. atgtickets.com/oxford