Detective Superintendent Barclay has a tough job on his hands. As the senior police officer investigating the mysterious disappearance of Leanne Wellings, the detective, played by Hugh Bonneville, is under pressure to find her – dead or alive.

With no leads and time running out before the 28-day police review – one of the “five days” of the title – all eyes are on Barclay to prove that he is in control of the situation and close to arresting the abductor. But, in reality, no one in Five Days is quite as they seem.

Hugh, star of many TV dramas over the last 15 years, including Tsunami, The Aftermath, The Cazalets, The Gathering Storm, Tipping The Velvet and Love Again, admits he was intrigued by the character and inspired by Gwyneth Hughes’s script.

He says: “Gwyneth writes so much for the character, rather than plot, and it’s nice to see the BBC breathing a bit and letting it explore characters as much as it has. Five Days is a slow burner,” he says.

The subject matter also hooked Hugh with twists and turns and different characters being suspected of the abduction – which is also being played out in the press.

“I love the fact that, ultimately, it’s got the whodunit format but it’s not really a whodunit, more of a where-are-we-at-and-why.

“It’s almost Dickensian in the complexities of the relationships and the way the characters overlap and the stories interweave – no one is going to be spoon-fed.

“There are often huge time jumps between episodes – sometimes it’s a couple of days and sometimes it’s weeks – so you have to keep up with it. I’m intrigued by it.”

Barclay, says Hugh, has not come through the ranks of the detective world – he has moved over from the traffic division.

“I think there’s a slight awareness that he’s not from the mould. He’s not been born into detective work, yet he’s clearly got quite a sharp mind and thinks laterally – he thinks outside the box. But he doesn’t suddenly say, ‘I know exactly who did it, with the candlestick,’ and all that.

“I think what this drama is quite bold and honest about is the painstaking way in which the police are obliged to work, and should work.

“Watching Life On Mars [the BBC police drama series set in the Seventies] really brought that out for me – that complete contrast with the kick-down-the-door, beer-swilling days of The Sweeney versus the way the police have to, and should, operate today.

“We see that at work in Five Days and it is very slow and deliberate. Barclay is a man who will only rely on evidence rather than pure hunches. However much the hunches cry out to be true, Barclay is pedantic, to a point, about wanting evidence and he feels railroaded into certain decisions.”

Aside from his enthusiasm for the character and the scripts, Hugh confesses that there was another major reason for taking on this project.

“I’d spent pretty much a year and a half working abroad [in the United States] and my wife said, ‘I want the next job you do to be within the M25!’ Most of Five Days is set in lay-bys around the M25, so it was very simple, really,” he laughs.

And does he think the drama will work for audiences on both side of the Atlantic?

“I think the HBO American audience will love it – it’ll go down really well over there because the story is universal. It’s really about the ripple effect of one potentially tiny incident which turns into a massive incident. Five Days shows the way it impacts on so many people.

“I think Americans will completely identify with this story – the only difference is that the cars aren’t as fast and the police don’t chew as much gum,” laughs Hugh.

Hugh has played a plethora of characters since his screen debut in the early Nineties, so it’s not surprising that this isn’t the first time he’s tackled the role of a policeman.

“I played a graduate police officer heading up a detective squad for the first time in a Murder Most Horrid with Dawn French.

“It was a great script by Ian Hislop and Nick Newman and the ‘murder most horrid’ bit was that Dawn’s character drove my character to a breakdown and eventually killed me!”

That rooky policeman, played by Hugh back in 1999, is obviously worlds apart from Detective Superintendent Barclay who, says Hugh, is “quite a loner and slightly an outsider”.

“I think maverick is perhaps a bit too harsh a word – it sounds like he’s got some sort of mad dynamic going on elsewhere. I think he’s just thoughtful and reflective and I’ve worked out in my own head what happened to him before scene one began, which no one else needs to know, but it sort of makes sense to me and makes me realise why he’s not quite down the pub every minute with everyone else.”