What really happened when Hodor's fateful Game of Thrones scene was filmed

The exterior of the Three-Eyed Raven's Cave was built in a quarry near Ballymena, Northern Ireland – a near-perfect bowl-shaped hollow now filled with scenery, tents and huts. The interior of the cave and the various tunnels were built in the studio in Banbridge and that is where we will spend the majority of our time. The walls are covered with moss and the floor is littered with real animal bones. On our first day we are also joined by 85-year-old actor Max von Sydow, who plays the Three-Eyed Raven – one of the old actors I love watching. Physically, Max appears to be more frail than even Margaret John, and I worry that he has been sitting in the cold for hours. But just like Margaret, he can fit into the role like an old pro.

Since returning to the series, this is the first scene where Hodor has to interact. Meera will talk to him about the food she dreamed about when they get home. The mention of home and sausages lights up Hodor's face.

It's supposed to be a nice, carefree moment before all hell breaks loose and the undead descend on us, but I just can't relax. In fact, I feel suffocated by the enormity of what is expected of me. Jesus fucking Christ, Kristian. You have to be on your A gameI say to myself, but I'm so excited that Jack notices I'm struggling.

“Are you okay?” he asks after a few takes, which I barely made it through. “Are you having trouble?”

“Yes, it’s terrible,” the words bubble out of me. I used to easily notice Hodor's subtle tics, but now I find myself tensing up when I try to express them. I explain to Jack the crazy journey I've been on over the last year and also the personal journey I've been on. I find it very difficult to immerse myself in anyone other than myself again. Then I'll stop. Did I just say all of this… to a director I don't know? I find. Years ago I would have remained silent, like when my back broke in the Great Hall. I stop talking and watch Jack's eyes carefully. Will he understand? Help me find out? Or fire me and move on?

“Okay, just take it easy,” he smiles.

“I’m fine, but everyone might need to be a little patient,” I say quickly. Jack squeezes my shoulder.

“Just relax. “It will all come back,” he reassures me.

Jack is right, just like John Ruskin was years ago. And after a while I start to remember: Don't think too much about Hodor; Don't think too much about your performance. As the morning progresses, Hodor reappears like an old friend.

[My stunt double] Brian is also worth his weight in gold. As soon as the magical shield that protects us in the cave disappears and the wights and White Walkers come for Bran, we have to free him as quickly as possible. That means shot after shot of me pulling Isaac on the sled attached to runners on the tunnel floor. Luckily, Brian will be directing a lot of these shots – shots where my face isn't visible. My back hasn't fully recovered yet and that also gives me the opportunity to concentrate on what lies ahead. Isaac has also become even heavier in recent years.