In the early hours of April 15, 1912, RMS Titanic sank to the depths of the Atlantic after colliding into an iceberg on its maiden voyage from Southampton to New York.

That night, 1,571 passengers and crew perished.

Linus Roache, who heads up a new four-part drama depicting the events aboard the liner, has a theory as to why interest endures a hundred years on.

"It's all the obvious things. I mean, it wasn't a war or a natural disaster, it was the human hubris of creating something and saying it will never sink, and it does.

"Then it's the question of what you'd do if you had two and half hours left to live," says Roache. "I think that fascinates us. That and the fact it was a microcosm of the world. When else do you have people of all classes, walks of life and nationalities shoved into one small place?"

The episodes are written by Downton Abbey's Julian Fellowes, who's sought to interweave the stories of everyone, from steerage and first-class passengers, to the boiler men and Captain, in order to tell the story of the whole ship.

Roache plays the Earl of Manton, and the 48-year-old actor's currently chatting over lunch dressed in the grandiose garb befitting an Edwardian gentleman of his rank.

It's been a long morning. He's only just finished filming emotional scenes aboard the impressive replica of Titanic, along with Europe's largest indoor water tank, within an epic soundstage in Budapest.

Not even the green screen that surrounds the set (the arctic views will be added later) can detract from the eeriness of wandering along the ship's Promenade Deck while hundreds of extras wearing period clothes and life jackets wait for their cue.

"The hardest thing to do is pretend you're cold," says Roache.

It is balmy inside the set, to the point that some cast have taken to using small electronic fans beneath their costumes.

Manton boards the boat with his wife Louisa, played by Geraldine Somerville ("As the story unfolds, you find out there's a bit of a secret. A dark underbelly to the relationship," says Roache), and their rebellious daughter Georgiana, played by Perdita Weeks.

They are just three members of an elite group who could afford a first-class passenger ticket (the equivalent today would be £61,000) but Roache is keen to defend his upper crust alter ego.

"He's not a stuck-up man, he's a little liberal, a little bit progressive and has a good sense of humour, which makes him more accessible," he says in a voice not too dissimilar to his famous dad's, who's known to millions as Coronation Street's Ken Barlow.

In preparation for the role, Roache worked with a dialect coach to capture the sense of entitlement of someone born into several centuries of aristocratic breeding.

"It was difficult to get into the mindset of a human being who doesn't have to worry about a thing, ever," says Roache. "There's no sense of having to struggle for anything. I can't relate to that. Most of us can't."

Rather than shy away from the inevitable collision, Fellowes faces it straight on. Certain scenes play out over and over, each time from a different angle and perspective, and the first three episodes end with the ship hitting the iceberg, while the fourth shows who survives.

"None of us know how we'd act in a crisis. We all like to think we'd be a hero but you'll never know unless you're tested. And Lord Manton turns out to be a man of action. Quite decisive, very responsible and really does do everything he can to look after other people before himself," says the actor.

A hundred years ago, the rules were simple - women and children first and it was predominantly men who perished in the freezing waters.

Asked what he thinks would happen in a similar situation today, and Roache says that while acts of chivalry may have lessened, he believes heroism survives.

"I think the best and worst comes out, but you'd probably still find people would step up to the plate and do the right thing," he says. "I mean, there are still stories of courage today. Look at United Airlines Flight 93 [on 9/11] and what those individuals did on the plane to try and save it. It was an expression of the triumph of human spirit."

Roache was only 12 when he first appeared on screen, as a boy dying aboard a ship in the TV series The Onedin Line.

Not long after, he earned a part playing Peter Barlow in Corrie opposite real-life father William Roache as Ken, where he simply "got the bug" for acting.

Credits now include Priest and Batman Begins, and he also had a previous brush with Titanic when he played kidnapped British journalist John McCarthy in the 2004 movie Blind Flight.

"For some reason we were shooting in the Belfast dockyard where they built the Titanic. I remember being there and thinking, 'Wow, this is spooky'," says Roache.

In recent years, he's enjoyed huge success in America with the TV series Law & Order. He now lives in New York with his wife Rosalind, but it's not out of the question for him to move back to the UK.

"I love living in the States, and feel very welcome and at home there, but I really do love coming back to the UK.

"The quality of the news, journalism and social commentary, some of the humour, the satire we have about ourselves - you don't get it in the States in the same way," he says.

Given the immense success of Downton Abbey in the US, it's little wonder he'd heard of the man behind his latest drama before signing up.

"Julian's perfect for the job. Much like Coronation Street and EastEnders, he draws mass audiences into stories about human beings and the small things that happen. This time he's managed to bring that into an epic situation," says Roache.

With Titanic marking his debut as a "top toff", Roache is only thankful for the wide-ranging roles he's offered.

"I've managed to cross a lot of genres and play many different roles. That's what I got into the business for.

"I like exploring and stretching myself in as many different directions as I can."