DESPITE having to film in the claustrophobic confines of a submarine for his latest project Ghostboat, it wasn't the problematic working conditions that David Jason found most difficult during the shoot.
Instead it was being away from his five-year-old daughter Sophie Mae, his child with Mirfield-born wife Gill Hinchcliffe - a hardship that not even being in agreeable locations such as Italy and Malta could allay.
Sir David Jason married his long-term partner in secret last December.
The happy couple announced the surprise news after the actor collected his knighthood from the Queen.
Daughter Sophie Mae was bridesmaid.
Gill, who met the actor while working at Yorkshire Television, is a former head girl of Mirfield High School - which is now Mirfield Free Grammar.
"That's the downside of filming now," says Sir David, 66. "It becomes more difficult because the child is growing up and these are, as everybody knows, very important years - the formative years - and you get a lot of fun from them.
"She, for example, apparently said to her teacher just before I was knighted last December, `I'm going to the Palace with my Daddy because he's being reunited with the Queen'," he laughs.
"Things like that are not going to last long once they get in command of their language. You're going to miss all that."
Sir David says that these days being a father affects the decisions he makes in his career.
"It's difficult because it is my job and something I enjoy very much," he says. "I'm certainly in a position where I will not do anything that I do not 100% believe in. I can afford to take some time out if I don't think a project is going to be a worthy one."
The filming of Ghostboat was also marred by another, more tragic, difficulty. Sir David was in the middle of the shoot when his old friend Ronnie Barker passed away last October.
"I got back from filming that day and was talking to my wife," recalls David. "I had a feeling she was not being as communicative as she is normally, and eventually she had to tell me. She didn't quite know what to do really because she knew I was filming and it would be such a big blow, which, as you can imagine, it was.
"So I was alone in this apartment in Rome and I felt very alone at that time because he was a very close friend and a great mentor of mine. It came as a shock to me as it did to everybody else. I phoned his wife immediately and left a message. We'll never get completely over it but he'll be with us for a long time to come in his shows."
All that aside, Sir David is extremely pleased at having pulled off an ambitious project like Ghostboat. A supernatural thriller of the kind more often seen on the big screen, the two-part drama, set in 1981 at the height of the Cold War, tells of the events following the return of a submarine that went missing during the Second World War.
Government officials enlist the help of Jack Hardy, played by Sir David - the submarine's sole survivor who remembers nothing of the events that led to the disappearance of both his boat and fellow crewmen.
With Hardy along for the ride they retrace the final journey of the submarine, with devastating results.
"Originally I wasn't going to be in the film," says Sir David. "I'd read the book and put forward the idea but I didn't read that there was anything in it for me. It was only when I presented it to producer David Reynolds and he said to me that Hardy was obviously my part that I began to think of it that way.
"I knew it wasn't going to be an easy ride. To work in those confined conditions day after day, 12 hours a day, it was very hot and sweaty. You do have to get on with your fellow man, I have to tell you. Fortunately not one bad word, not one moment of irritation, came from anybody."
Sir David discovered the book, by American writers George E Simpson and Neal R Burger, while filming an episode of A Touch Of Frost. It was a prop that he `borrowed', and he was quickly absorbed by the story.
But given the expensive nature of transferring such a story to the screen - Sir David says the effects cost £1,000 per second - it took a lot of persuasion on his part to get people to back the project.
"Not long before I read the book I'd read an article written by a critic, saying that British television is now very formulaic and all we seem able to do is hospital series, police series, reality shows and that sort of thing. It asked, where was the inventive, creative television we used to have?
"This was bearing on my mind, because having enjoyed, and the audience having enjoyed, Frost I thought perhaps we were a bit guilty of this. Then I found the book and thought it was a really exciting yarn. I wondered whether this is perhaps the sort of thing the critic was talking about.
"It was not an easy task to convince people to do it, either. We took it to the heads of everywhere. It's a wonder we didn't take it to the Prime Minister to try and get some money out of him, but fortunately we were supported by Yorkshire Television and ITV."
What probably helped Sir David get this project off the ground is his status as one of the country's most popular and best-loved actors, something which was underlined when he became a knight of the realm last December.
"The only thing I would say," he says of the day, "is that the image we all have of getting knighted is that you go down on one knee as mister and you rise as sir, and the Queen says, `Arise Sir David'. Well, she didn't.
"It's rather a shame really. She just does it and you get up and she puts the gong round you. She does have a few words with you and I'm not at liberty tell you what she said, but I thought it was rather sad because I was expecting it.
"And I got married the day before as well, which was delightful, I've been told to say," he laughs. "We thought it would be a nice way of marking it, and I didn't want to make too big a fuss."
Next for David is another series of A Touch Of Frost, and another ambitious project in the form of Hogfather, the first Terry Pratchett book to be adapted for the small screen. As for whether he'll make a return as Del Boy in Only Fools And Horses, he remains vague.
"Bless it," he grins. "We'd love to do more but tempus fugit. You can look that up in the dictionary."
* Ghostboat is on ITV1 tomorrow and Monday April 10.