Warning. Once you've watched upcoming BBC thriller Nightsleeper, you may not want to take the train for a while. And for once, it won't be because of high prices, delays, cancellations and having to stand from Manchester Piccadilly to London Euston.

Nick Leather's high-octane six-part series follows a runaway sleeper train full of passengers which has been "hack-jacked" in a cyber attack and is on the road - or should we say rail - to goodness knows where. And it's down to ex-cop Joe (Peaky Blinders' Joe Cole) and acting cyber security chief Abby (Alexandra Roach) to stop it in its tracks.

"I tried to avoid trains for a little bit after [filming]," Cole half jokes.

"I think they offered me a train home. And I drove back the long way from Glasgow after we wrapped!"

Leather, whose previous work includes The Control Room, Murdered For Being Different and Mother's Day, says he first had the idea for his latest drama seven years ago.

"I always fancied doing something in real time, the technical challenge of it. If there was an attack on the rail network, could we then localise it on one train? And then suddenly we have a modern Murder on the Orient Express and a bit of Speed... and we make it completely up-to-date," he explains.

"It's a six-part series so what journey takes six hours? The sleeper train from Glasgow to London."

He even spent the night on the Caledonian Sleeper as part of his research.

"I also had the Network Rail map of Britain on my wall for a couple of years. You get obsessed with these things!"

But could a hack like this happen in real life?

Nothing is "unhackable" as such although this kind of scenario is fairly unlikely.

The closest we’ve come to this happening in real life is in Poland last summer when a series of sabotage attacks brought trains to a standstill. The attacks weren’t really computer hacking – they tricked systems into shutting down as a safety precaution by sending out a series of tones over radio signals.

In this show, the criminals manage to install a physical device to the train to carry out the hack. But the hackers would need physical access to the driver cabin which is arguably even less easy than trying to hack a train remotely.

Cole and Roach's characters have to work together to stop the impending train wreck, with Joe on the train trying to disable the hacking device placed in the control room while Abby and her team frantically try to work out who is behind the "hack-jack" from the National Cyber Security Centre.

Strangers until the crisis hits, the pair communicate on an unreliable satellite phone as they desperately try to save the lives of those on board.

The tension is palpable but it's frequently undercut by the drama's very British sensibility, namely dark humour.

"I thought it was just a really fun, proper, authentic British drama," Cole says. "Some of it's a bit silly... some of my lines... you could read them, in a way, cheesy and I was like, OK, this is going to be fun."

"I did Skins back in the day, and there was some absolute cheese on toast with a slice of halloumi in that. And I remember enjoying the challenge of saying some of the more ridiculous lines and pulling them off.

"I've been on many sets where actors [say]: 'I can't say that. We've got to change it.' And often it does get changed. I actually like the challenge of trying to pull off the more crazy lines."

Roach adds: "As British people that's what we do, isn't it? When we're tested under pressure it's to find those moments of humour... that's what makes us human."

Leather concurs: "It's how we respond to a crisis, there’s got to be a lot of gallows humour there – if we don’t have that and it’s cod-American, it’s not going to work. It has to be the British way. And we love to moan about trains!"

He adds: "I’ve always liked Hollywood thrillers, the guilty pleasure, the escapism of it. It's melding the two very different styles together (US thriller with British drama)."

The high-end special effects are certainly more in keeping with Hollywood. Without giving too much away, there are some impressive action sequences on the track.

“We got together a really big budget and got great people in [the Flying Colour Company] to do that work," Leather says.

“When they look out of the window [of the train] the world is whizzing by at the right speed... the actors kept getting travel sick even though it was filmed in a warehouse in Glasgow!”

Leather is known for creating authentic, down-to-earth roles, and while the action scenes may be other-worldly, he is still passionate about wanting his characters "to come from normal backgrounds".

His writing heroes include Jimmy McGovern, who he has worked with previously, and Alan Bleasdale.

"I want Abby to feel relatable, I can’t relate to someone who doesn’t get scared, I want her to be a relatable hero," he says.

Roach adds: "I did a lot of research on the hacking community and the cyber world, (and realised) how male dominated this world still is.

"For Abby, coming from south Wales from a working class background, she’s not your average cyber security worker. To get to that place she’s had to show a lot of resilience, ambition and tenacity in this world that she doesn't really always fit into."

Roach made a conscious choice to use her native Welsh accent.

"You hear it more in the comedy world but in the drama world, you don’t. It was an important choice that I made to stick with my own accent.

But her favourite trait?

"She's so instinctive, she never really takes the safe road."

Leather says: "There's a Gary Cooper line in High Noon where he's going to avoid the showdown and he says 'I thought about it because I was tired' but he stays. That's all my characters, I want them to think about not being the hero."

All six episodes of Nightsleeper will drop on BBC iPlayer at 0600 BST on Sunday 15 September. It will also air on Sunday and Monday nights across three weeks from 21:00, also starting on 15 September.