Threads and Game of Thrones among TV's most shocking moments

*Spoilers for Game of Thrones season one below*

From gut-wrenching revelations to murders no-one saw coming, television writers have long understood the power of shocking their audience.

Sudden deaths, surprising reveals and tragic talking-points all drive controversy and conversation among drama viewers. As do eye-wideningly dark on-screen events.

We asked members of our Screen Babble discussion group on Facebook to pick their most shocking TV moments. Here's what they had to say.

'I don't think many kids slept well'

When gritty British drama Threads aired on the BBC in 1984, it sent shockwaves across the nation. Imagining people fighting for survival after a nuclear strike, the sight of an atomic bomb hitting Sheffield proved too much for some.

Karen Dunn, watching as a young teenager at the height of the Cold War, recalls the moment "scared the living snot" out of her.

Britain in chaos: Threads painted a stark picture of a post-nuclear Sheffield

"We were being warned about the devastation which could be caused by cruise missiles, there had been a false alarm in the Soviet Union about the launch of US missiles, and the missiles at Greenham Common were always being featured on the news.

"Quite frankly, I don't think many kids slept well for weeks after seeing Threads."

The not-so-Happy Valley

Another Yorkshire-set TV show adept at shocking was acclaimed crime series Happy Valley. Nick Mitchell highlights a desperate, vicious fight between Sarah Lancashire's copper Catherine and villain Tommy Lee Rocye in season one ("a brutal, hard-to-watch moment in a dark but great show"), while Sue Dougall still flinches at the memory of the scene where Royce runs over a young policewoman.

Game of Thrones: the king of shocking deaths?

(Warning: spoilers for Game of Thrones season one below)

One show comes up time and time again when it comes to characters being brutally and unexpectedly killed off. And that show is Game of Thrones.

The epic swords and scheming saga, itself based on the convention-defying fantasy novels of George RR Martin, arguably changed the TV drama rules when it landed in 2011. And it was all due to the death of one beloved protagonist.

"For me it has to be Ned Stark's death in Game of Thrones," says Linsey McQueen Carson: "He is a major character - really cool, charismatic, all round good guy and family man. Then BOOM! Dead."

Alan Clark agrees that Sean Bean's amiable Northern Lord getting the chop shook him. "I think it was the first time I had seen such a major character of a show killed off so soon."

"It was a 'WTF-just-happened' to such a main character moment," Saleha Lokhat adds. "Never saw it coming in a million years."