By Fiona Pryor
Entertainment reporter, BBC News
Daniel Radcliffe, Kim Cattrall and David Haig helped mark Remembrance Sunday in an ITV film about World War I.
Daniel Radcliffe discovered his great-uncle had fought in WWI
My Boy Jack told the story of how author Rudyard Kipling (Haig) used his influence to get his son Jack (Radcliffe) a commission with the Irish Guards.
The 17-year-old had initially been turned away from the services because of his poor eyesight.
Previously a stage play written by Haig, the script was adapted by the actor so it would work for the small screen too.
It took him 22 years of research and writing to bring Kipling's story to life.
Harry Potter star Radcliffe, 18, was not even born when Haig first started developing the idea.
"It's quite amazing that something that has taken 22 years has culminated into 27 days filming," Radcliffe said.
Haig was inspired to write the play after reading the writer's biography and seeing a picture of him.
"I had this uncanny experience of looking at myself," Haig explained. "The resemblance is extraordinary, almost unnerving."
The strange coincidences continued throughout filming.
"Daniel's birthday in real life occurred while we were toasting an absent Jack's birthday as the Kipling family," Haig added.
The last day of filming at Bateman's - Kipling's family home in East Sussex - co-incided with Jack's birthday.
The 22-year project took just 27 days to film
Radcliffe also discovered his great-uncle had fought in World War I.
Jack went missing in France after just two weeks of service, and his parents spent months trying to find out what had happened to him.
Gradually, as they pieced together the truth, Kipling was forced to face the fact it had been because of him that his son had gone to war.
"I'm interested in the individual devastation that a single loss in a war creates and the collateral damage to family, friends, relations for generations to come," said Haig.
"One single loss does that, and, on the morning of Jack's death, 7,500 soldiers set off equal chain reactions of destruction within families."
Haig said his research, which involved reading as many biographies as he could, and studying the diaries of Kipling's wife Carrie (Cattrall), meant the portrayal was as "honest" as he could have made it.
David Haig said he thought his likeness to Kipling was 'uncanny'
That made filming especially gruelling for Radcliffe.
"When you're actually in the trenches and it's freezing cold and there are rats everywhere, that does make it slightly easier to imagine yourself into that situation," said Radcliffe.
"But equally you can't ever hope to fully comprehend what it was like to be there."
The crucial scene where Jack is sent over the top into No Man's Land was particularly hard work for the star.
Before filming the explosion scenes, Radcliffe was told his visibility would be reduced by 70% because of the smoke.
"When the explosions did go off the air was just filled with dirt and for about five seconds you could see nothing and you were sort of running blind," he said.
Exterior shots of the Kipling house were used in the film
"I think those five seconds were the closest you ever really came to experiencing what it was really like," he added.
Despite being born decades after war was declared in 1914, Radcliffe is very clear about why he signed up for the film.
"You realise boys of Jack's age are still going to war and that's why I think the film will have resonance for that reason," he said.
"But not even just for that reason, the tragedy isn't just about the war, it's about the idea of the parents outliving the children, which is the greatest tragedy imaginable really.
"For me the thought of forgetting all the people that fought is terrible.
"I suppose we just need to make the effort to remember them and realise how lucky we are to not ever have to endure those conditions again."