Sean Harris stars as deranged killer Stephen Morton in Southcliffe. (Channel 4)

Television has become increasingly morbid this year. From Run to The Returned, our screens have been filled with gritty dramas exploring how people cope with grief and the darker side of human nature. But new Channel 4 show Southcliffe is by far the bleakest of them all. Taking inspiration from real-life small town shootings such as Hungerford, Monkseaton and Dunblane, this astounding four-part drama looks at the scars left behind on the eponymous town's residents after it is transformed by tragedy.

Penned by Tony Grisoni, whose previous drama Red Riding depicted a savage Yorkshire police force in the 1970s, Southcliffe is set in the repressively flat and mundane surroundings of modern day Kent. Other than the nearby nuclear power plant, it is the ordinariness of Southcliffe, and the intelligence and subtlety with which the subject is dealt with, that makes the story of a shooting spree neither sensationalist nor exploitative. Captured often in wide shots with a palette of earthy green and browns, and noticeably absent of any background score, the tone of Southcliffe is on the opposite spectrum to the picture postcard murder mystery of Broadchurch.

That's not to say that the show is dull. Rather than a typically stilted kitchen sink drama, Southcliffe maintains an unbearable level of tension as events unravel before your eyes, with the real-time nature in which some scenes are filmed markedly cinematic in scope.

This is in no small part down to Sean Durkin, the American director who made his breakthrough last year with film Martha Marcy May Marlene, and has made a surprising career move in opting to follow up that indie hit with a four-hour drama for British television. With esteemed filmmakers Martin Scorcese, David Fincher and Jane Campion all directing for the smaller screen in recent years, Durkin argues that the transition from film to television is no longer noticeable. "The whole preconception that making TV is different to film is ridiculous," he said. "You're filming drama with great actors, so there is absolutely no difference".

The show comes brimming with an all-star cast that bring Southcliffe to life. Sean Harris is sublime as Stephen Morton, the deranged loner who finally snaps and goes on the rampage throughout the town; as is Rory Kinnear as David Whitehead, the journalist still emotionally scarred from growing up in Southcliffe and who has to return to cover the carnage. Shirley Henderson, Eddie Marsan, Joe Dempsie and Anatol Yusef make up some of the other residents who are all personally affected by the tragedy. Kinnear, who has starred in other high profile television hits Black Mirror and The Hollow Crown, explained why he was drawn to Southcliffe. "I have an interest in the ordinary, and in how people cope with disaster," he said. "This story could have been told in such a different, more sensationalist way, but with Tony and Sean I just felt like I was in good hands."

The market town of Faversham stood in for Southcliffe in the series, and despite the fears of local residents that the cold violence of the show will damage tourism, the lack of identity given to the setting suggests that this could happen anywhere in England. Southcliffe is a town riddled with suppression, where previous troubles and dark secrets are buried deep down until the mass murders make its citizens take stock of their lives. New York-based Durkin, despite being an outsider, said that he hoped his vision struck a chord with British people watching the show. "All I ever want to do is create truthful moment after truthful moment. That's what directing is about; capturing something that is honest and engaging and I hope I have done that," he said.

To say Southcliffe is uncomfortable viewing would be a grave understatement, but the show is evidence once more of the increasingly bold steps television drama is taking; creating programmes that trouble the viewer instead of just entertaining them. With mindless blockbusters such as Pacific Rim and Man of Steel in the cinemas, the refreshing realism of Southcliffe makes it the most provocative thing you'll see all summer.

Southcliffe premieres at 9:00pm, Sunday 4 August on Channel 4.