Kimberley Nixon says she is a mega murder mystery fan.

What is Laura like?

She's lovely, she's very sweet and sort of put-upon, and she's a carer for Moira who is a bit of a tyrant of an employer.

How bad is Moira really?

She is pretty bad! I mean, even when we're in the back of the shot, she's always doing something quite bad. I think Moira's one of those people that thinks if she is paying you, she can treat you exactly how she wants, there's no need to treat you like a human being.

How have you and Nina Wadia, who plays Moira, worked out how to play that relationship?

I think we sort of accepted that if Laura didn't try and help her into her seat, she'd kind of go, "What are you doing? What am I paying you for?" kind of thing. But the moment she does try to help her, she's batting her hand away. So Laura can't win either way. I think physically, Laura is quite timid and doesn't really know what to do. The way Nina is playing her, she's so formidable, there's an aura of anger around her.

Is it the case that anybody could be the suspect?

Yes. I think that's the kind of best whodunnit. There are a few that seem more likely, you think, to have done it, but then you think, "Oh, it's so obvious, it can't be him," or, "Oh, she's so unlikely that it must be her."

How comedic is it?

I think there's a couple of characters that are a little bit larger than life, like Griff Rhys Jones as the writer, but there's also a couple of more straight characters. I think we're all playing it like a good murder mystery farce. This would be an amazing cast to do a stage play, but we'd never get through it, there's no way - the corpsing on this is the worst I've ever experienced!

And I know they're going to try and blame me, but it's not me! I mean, Johnny Vegas and Sian Gibson can barely get through a scene together. It's kind of like a domino effect, especially if we're doing a scene with all 14 of us. There have been some days where we genuinely didn't know how we were going to get through it. So it was really fun for us, but so annoying for the crew, they basically hate us.

Had you worked with any of the cast before?

Griff! Last year we did Ordinary Lies for the BBC. We were both in it, but we were never in it together. And Jason Cook, who wrote this, wrote Hebburn, which I was in, so that's another connection.

It's an amazing cast. I think I got cast a little bit earlier on, so the names kept coming through and it was like, "Oh, I think Johnny Vegas is the bus driver," and "Oh, Sian's going to be the tour guide," and, "Una Stubbs is in it!" And then Nigel Havers. It was just ridiculous, just a dream, fun cast.

And do you get on well with Sian?

She's brilliant - she's very fun. We're like the two Welsh girls. So she's North Walian and I'm South Walian, so we keep the boys in check.

Is there rivalry there?

No, I can take her, she's tiny. She's like, five foot. I can definitely take her.

Do you enjoy a good murder mystery?

I am a huge, mega murder mystery fan, to a degree it's probably quite unhealthy. Like, really unhealthy! All the tables at my wedding were different detectives. It got weird pretty fast!

What was the top table?

Poirot.

I've basically begged my way into any murder mysteries. I've done Poirot, Marple and Midsomer Murders. I was so desperate to do it, I offered to do Poirot or Marple as a maid in the background for free, and my agent rang up and said, "You cannot tell people you will do things for free!" That's why I really love, the kind of traditional element of all of this. Because it's my two big things - murder mystery and comedy - coming together, so literally my ideal job.

So Murder On The Blackpool Express was everything that you hoped for and more?

Yes, literally! Just such an ideal job. Everyone is so lovely and funny, and we just don't stop laughing for 10 hours a day, even though we're all trapped on a coach and it's boiling hot and all sweaty and gross! And you couldn't find a group of less professional actors than this, basically...

You are in a perfect position then, to tell us what is the ideal murder.

Stab someone with an ice dagger. It melts, and there's no fingerprints. Or, another one, blood bullet... Get the victim's blood, freeze it into a bullet shape, shoot them, it just dissolves into their bloodstream.

The Murder On The Orient Express movie comes out at around the same time as this. Which is going to be better?

Well, I don't think Kenneth Branagh can compete with Johnny Vegas, so I'm just going to leave that there!