(Pocket-lint) - Before we write another word, stop reading here if you haven't seen Game of Thrones season 5 yet and, specifically, episode 8 "Hardhome". There be spoilers ahead, aaarrrggh!

If you've made it this far, on your own head be it...

Hardhome is by far and away the most dynamic and awe-inspiring episode of Game of Thrones since The Rains of Castamere and the Red Wedding goings-on. Not only does it show more of the wildlings and what is occurring beyond the wall, including some incredible effect work on a wildling giant, but it has the best battle sequence we've seen in TV history.

White walkers and zombies appear in vast numbers, swarming over the inhabitants of the camp and the scenes show just how big a threat the undead will be to Westeros in future.

You cannot help but marvel at the sheer scale of the scenes, with thousands of undead creatures on screen at once in what must have been one of the biggest budget episodes yet.

READ: Game of Thrones exhibition in pictures: Winter is already here

Now we can see how some of the effects were created thanks to a behind the scenes video posted by FX company El Ranchito Imagen Digital.

It shows the original locations and the layers of snow and zombies added in post production. Even mountain ranges and lighting were added in post. The project was quite simply huge.

Again, if you haven't yet seen the episode, don't spoil it for yourself by watching the video below. But if you have, we thoroughly recommend you give it a viewing. It's amazing how some of the pieces were all brought together.

Writing by Rik Henderson.