Sir David Jason's unrivalled talent for comedy roles was indispensable when it came to playing Harry, a man he describes as "a funny and sometimes tragic old codger."

"There were times during filming when I'd say to David Warner, who plays Frank, 'Look at the pair of us, we're like Laurel and Hardy!' He was the grisly old git constantly complaining and winding Harry up and I was the character absorbing it all, until I'd finally had enough."

"There was a lot of laughter involved, but a lot of pathos too. At one point, Frank has driven Harry so mad with his constant goading that they end up in a field, squaring up to each other trying to land punches. But the pair of them have got so many health problems and are so old they can't even fight. On one level it makes you laugh, but on another level it's also very emotional."

A good description, perhaps, of the comedy drama in general, which Sir David hopes will both amuse and move the audience.

"I suppose I'd really describe Albert's Memorial as black comedy with very serious undertones. It's meant to be amusing because here are two old codgers stealing a friend's body because they promised him on his death bed. Then they cart him off to Germany on the top of a taxi, bickering and bouncing off each other all the way. But beneath the laughs there are so many serious issues. For example, the futility of war, the terrible things that we do to each other in its name and our persistence in hating and killing each other in conflicts even today. Why can't we just stop it?"

"Then, of course, there's the whole subject of friendship and how it is that these two old boys, who drive each other mad, have managed to stay friends for decades. What binds them to each other and also, of course, to their dead friend, Albert? What starts as a bit of a caper, becomes quite an emotional journey as the story of what happened to the three men during the war is told through flashbacks. All of them shared a devastating experience and they've lived with the guilt of it ever since. It's bound them together but also really spoilt their lives on many levels. Albert's Memorial is partly about that guilt, but it's also about forgiveness and laying the past to rest. For me it was always going to be a story that was so much more than just an entertainment."

The actor, who has starred in many iconic TV series, including Only Fools and Horses, The Darling Buds of May and Open All Hours, recently said goodbye to the role of Inspector Jack Frost, the curmudgeonly detective he played for 18 years. Much as he always loved the character, he says, he enjoyed getting under the skin of an entirely different persona like Harry. "Frost was much more contained and in control. Harry is unravelling, which is always interesting to play."

More of a hardship, he says, was being on the road filming for six weeks. "You're not just away from home, which is hard in itself, but you also have to spend every day and every evening with the same people. On Frost, I always had a little cottage that I lived in during filming and it was great to be able to close the door at the and of the day and then come back in refreshed, whereas when you're on the road it can be a bit intense. From that point of view, it was very fortunate that all of us managed to get on so well, it would have been a nightmare otherwise."

The latter applies to all three of the main stars, including Judith Hoersch, who plays Vicki, the mysterious young woman who joins them on their journey. "Judith is a lovely, charming young woman," says Sir David, "and one of the nicest things was that the three of us were able to be generous with each other and have a good laugh. Nobody was remotely grand, and given David Warner's CV, he might have had the right to be. None of us had pretensions of any kind. So, it was a very happy band."

Born in 1940, just six months after the declaration of war and raised in bomb torn London, Sir David admits that Albert's Memorial felt, in many ways, like a very personal project.

"I suppose that I just grew up knowing, in a very vivid way, that if it hadn't been for the men who fought in World War II we'd all be living in a very different world now. I feel that we own a debt of gratitude to men like Harry, Frank and Albert and Albert's Memorial is a small way if acknowledging it."

The characters themselves, he says, are fictitious and the specific story that is told isn't true, per se. But what happens in the story is based on some shocking real events that have stained the pages of history. In the end, the more grisly, shocking element of the tale is told through the filter of entertainment.

"What we've done is to try to tell the story in a way that throws some light on some terrible events that have largely been hushed up in history books. And we haven't been coy about the way we've done it. But, he says, the human experience is never just all darkness, there is always light too and sometimes the funniest moments come out of the saddest situation. In Albert's Memorial they certainly do."