Game of Thrones producers pulled out all the stops to ensure last night’s battle beyond the wall was the most jaw-dropping to dateCredit: HBO

The ‘frozen lake’ in last night’s episode was made from concrete in a Belfast quarryCredit: HBO

The cast filmed the visually sumptuous scenes north of the wall in Iceland, with the remote surroundings only accessible by heavy duty 4x4s.

Actors Rory McCann (The Hound), Joe Dempsie (Gendry) and Paul Kaye (Thoros) admitted to being awestruck by the scenery which contained pale blue glaciers and snow-covered mountains.

For the frozen lake battle itself, the team decamped to Wolf Hill Quarry in Belfast, Northern Ireland, where they crafted a “lake” made out of concrete.

They painted the hillsides and used some 3,000 bags of snow blown through six machines to transform the set.

The effects team built a false floor above a tank in the studio for when the wights crashed through the ice into freezing cold water for extra authenticity.

Two of the most memorable parts of the battle saw Jon Snow’s team of rogues attacked by a zombie polar bear and Daenerys’s three dragons setting alight the Night King’s army.

man in a green suit played the role of a zombie polar bear by manipulating a flaming contraptionCredit: HBO

Emilia Clarke clung on to a large foam structure representing her dragonCredit: HBO

A rig was set up to propel a stuntman through the air so he could mimic being violently tossed from side to side by the beast, while a man in a green suit played the bear by manipulating a flaming contraption.

Back in the studio, Emilia Clarke sat atop a huge piece of green foam representing her dragon as her co-stars clambered up to join her.

fake icy floor was set up above a tank of water in the studioCredit: HBO

Jon Snow and his team hurtled across a fake lake made from concreteCredit: HBO

The actress admitted she liked a challenge but said pretending to fly a powerful dragon was unlike anything else.

Despite the incredible attention to detail put in by the team, not to mention the huge budget – the episode wasn’t gaffe free.

Eagle-eyed viewers noticed a wildling fighting with Jon Snow flailing his weapon at an invisible enemy despite the group being surrounded by wights.

wildling was spotted swinging his weapon at an invisible enemy in a CGI fail from last night’s episodeCredit: HBO