Can you talk us through your characters? They're quite an unusual pair...
Nigel: I'm a doctor and I look after my brother Kevin, who has memory difficulties. In fact, he can't remember anything for more than five minutes really.
Kevin: He's kind of like a human goldfish. He was hit by a car some years back and he's very happy but just not entirely in possession of all the facts all the time.
Nigel: He can't really be left alone and I have to be with him all the time, so that's the story really.
That feels like a good device for a murder plot...
Nigel: Yes, and everyone has something similar. Anybody on this coach could be a suspect, and is to a certain extent.
Kevin: So we can't give anything away because one of us, or both of us, might be the murderer, or a victim, or both, or neither.
In terms of tone, how do you see it?
Nigel: A comedy. Do you agree with me?
Kevin: No. I think it's the one of the most searing tragedies that has ever been put on British television. Yes, it's certainly a comedy, there's some very recognisable characters, and some new characters. And yes, it's very gag-heavy, there's lots of good jokes hopefully, and a wide variety of very entertaining characters.
Nigel: I would say it's quite a classical piece in that respect, and it's been shot in a very traditional way, with minimal movement from the cameras. I haven't noticed anyone with a steady cam or hand-held camera. That's not the normal way these days; everyone likes to throw a camera over their shoulder and leap in. But they aren't doing that. So there's something sort of 1950s about it. Miss Marple-ish.
Kevin: Yes. There's shades of tales of mystery and suspense about it, I think, which was around the 70s or 80s, wasn't it? So yes, it's got a kind of classic feel about it, if you like.
This is going to be out in the same month as Murder on the Orient Express, the big film version with Johnny Depp.
Nigel: I think we'll do better than them. I saw the trailer. I think we've got a better film. Have you seen Kenneth Branagh's moustache?
Kevin: I haven't. Do you think it's going to get its own Oscar?
Nigel: It might well get its own Oscar!
Kevin: Is he playing Poirot?
Kevin: Oh, why haven't they gone for Suchet?
Nigel: I wouldn't know. Pass. Kenneth Branagh is directing it, producing it and starring in it. So I would imagine he wanted the main part.
Kevin: Yes. He likes to keep busy.
You have a great cast: do you think you hold your own against Johnny Depp and Daisy Ridley and Kenneth Branagh?
Nigel: I don't think that's any competition at all, frankly, do you?
Kevin: None at all.
Nigel: And to be perfectly honest with you, more people watch the television than go to the cinema, so with us in it, it will be a big night.
Kevin: Yes, of course, it will be a big night. I'm thrilled to be working with Nigel of course, but also Una Stubbs, who, throughout my life, has just been a wonderful thing happening whenever she has appeared on television. She's a wonderful phenomenon but apart from that, a really lovely person as well.
Nigel: Everybody's famous in this show.
What was Una's show that you loved the most, or what was your first memory of her?
Kevin: I don't know... everything. When I was a kid, Summer Holiday was on every holiday, and I remember the Cliff Richard shows in the early 70s, and I remember her in Worzel Gummidge, actually, I loved that, and I remember her making a quite early appearance in a much under-rated, barely-known sitcom from 1960 called The Strange World of Gurney Slade, and I found out that Una hadn't seen it, so I got hold of a copy for her from 1960. And of course, when you meet somebody and you've always liked their work, and they turn out to be lovely, that's wonderful. Excellent.
Nigel: I hadn't really met Griff properly. It's got to the stage now that I'm going to be staying with him after filming. He has a house in Suffolk, I said I'm going that way, and he said, "Well, you must come and stay." So that's come in handy, that hotel can be cancelled. I was a massive fan of Not the Nine O'Clock News and I'd never worked with Griff before.
There must be so much gossip swapped back and forth...
Nigel: Well, to be honest with you, the film is interfering with our socialising. It interrupts the flow of what we really want to do.
Kevin: Yes, you can't really hope to finish a decent anecdote without being dragged away to film.
Nigel: Yes, it's really annoying. So now we carry on regardless with the anecdote. They might say 'action' but we ignore them and finish the story and then say, 'Sorry, starting now'.
Kevin: A few of the anecdotes might make it into the finished film.
What do you think the coach element adds to the comedy?
Nigel: It only cost £8000. I'm surprised we got anywhere in it! It hasn't got air conditioning or anything. You wouldn't want to sit in it for too long with the engine on. It would turn into a real murder mystery.
Who is your favourite detective of all time?
Nigel: My favourite colour is blue, just in case you ever thought of asking.
Oh, it must be Sherlock Holmes...?
Nigel: To be honest, Jeremy Brett is my favourite. Jeremy Brett was a wonderful actor, and I loved his Sherlock Holmes, he was just stunning, and I think the way Granada did them was just incredible. On practically no budget. I always wanted to be in one, but sadly I never got asked.
Kevin: I love Colombo. I don't know if he's my favourite, but he's certainly up at the top there. I just loved the whole character, and watching them when it was first out, I just thought he was so funny, and I loved the way that he hid himself behind that shambling exterior when he knew exactly what was going on. I thought that was very funny.