See How They Run murderer star explains their inspiration

And the cast member who plays the killer has spoken to RadioTimes.com about their inspirations for playing the villainous role, including what music they listened to in order to get in the right headspace for the part.

If you've not seen the film yet, then beware – there are major spoilers for See How They Run from here on out, so only read on if you're happy with finding out the identity of the murderer.

If you're still reading, you'll know that the killer is revealed to be Dennis – the character played by This Country star Charlie Cooper – with the theatre usher looking to get revenge after claiming his own personal story was being exploited for entertainment by Agatha Christie and the others involved with the production.

Speaking to RadioTimes.com in an exclusive interview, Cooper revealed that he hadn't been told prior to first reading the script that his character was going to be the murderer.

"He [director Tom George] didn't tell me," he said. "So by the time I got to the end, I was like, 'Wow, that's pretty cool.' It's just such a nice surprise, and something I always would have loved to have done."

Asked if he looked to any particular movie villains for inspiration, Cooper explained: "Do you know what, I don't think I did. I should have done – but I listened to a lot of villainous music!

"Have you ever seen Basil, The Great Mouse Detective? It's brilliant. But there's a rat in it called Ratigan, and he's like the best Disney villain you'll ever see. He really inspired me."

Meanwhile, Cooper says that he hopes fans don't guess that he's the real murderer too early into the runtime, claiming that he "always gets annoyed with people who crack it immediately".

"My girlfriend always does and I take ages to find out," he said. "You know, it's not until the end that I know who it is, I always fall for the red herrings.

"You want people to be at it until the very end, hopefully. It's so difficult [in] murder mysteries – it's so sort of mathematical in a way. It has to be so finely balanced because you just can't give it away too early, and if you're dissatisfied with the ending and who it is, you're like, 'Oh, well, we didn't see them enough earlier, you could just make anyone the killer.'

"So, that balance is so, so crucial. And I think they really discovered that during the edit."

Now remember – now you have read our interview, you are an accomplice to a murder, and so we ask you to remember that it is very much in your interests not to tell a soul whodunnit!

See How They Run is out in UK cinemas now. Check out more of our Film coverage or visit our TV Guide to see what's on tonight.

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