This is a hugely ambitious project.

The design department is extraordinary, I mean just extraordinary.

The scale and the level of detail is so incredible.

It's like being in a brilliant, psychedelic disco sometimes.

In that kind of frozen north sort of way.

Biggest problem with this story is how crazy and fantastical and amazing and kind of vast it is.

You have to curate everything.

So it's not as easy as just propping it with standard stuff, you know.

Each area and each space has been quite carefully curated to tell the story.

Pretty much every chapter in the book is a different world.

It keeps travelling. Lyra goes through so many different forms

of existence and worlds, so it's a huge job for the design.

It just shows the amount of respect, I think, that people have for the project

that the producers have gathered together this incredibly talented group of creatives.

You get the chance to have real life grown up playgrounds

to inhabit and populate the world of make believe.

And that just adds such joy.

Asriel's lab has so many little things, they are so detailed.

It's like they have every single switch.

It actually really helps acting-wise.

We've had such vast, complex builds on this show.

From oxford elements, where we did vaulted ceilings and everyone

was looking in the rushes and going 'this looks real, wow!'

Mrs. Coulters apartment in London is terrifying 'cause it's in her likeness,

Mrs. Coulters likeness and her monkey.

But I don't think you would know it until you spend a few days there and then you're

like oh, this place is kinda creepy.

We built an entire town on the Brecon Beacons.

It was an amazing feat. It was literally a whole town with interiors, exteriors, a dock.

And it was for one episode and I think it's very exciting.

Trollesund in particular has been my favourite because you really are transported

to a small, gritty, hardbitten, dangerous outpost somewhere far, far away in the north.

And they've got half a dead whale and the blubber machine and it's just all so real and visceral.

It just blows my mind.

Just the scale and the level of detail is so incredible. It's exactly what you want when you're fulfilling

a fantasy world that so many people have imagined in their own minds.

I was looking in a window, and there was like lentils or something,

but it had a label that how much these were.

Now that was never ever gonna be featured, but someone had taken the time to do all that.

You think it doesn't matter, you think well nobody's gonna see that, but actually it does matter.

What is it?

It's an alethiometer.

I love the alethiometer. It's brilliant, it's really heavy.

I actually had the shoulder bag from Mrs. Coulter's episode.

It kept on breaking because of the weight of it.

But it's amazing. It has literally all of the drawings, you can like move the needles.

This was another bit of a design journey because of what it means to the audience,

what it means to the book. And with the alethiometer

there wasn't really a conscious decision to make it not round, 'cause it is kind of round

as it were. But there was a kind of feeling I had that I didn't really want it to look

like a victorian pocket watch. Ironically, I was trying to find something that probably

was not inside the mind of the fans i.e. round for a start, because I wanted to explore the

shapes and feelings and sizes.

It wasn't to be controversial it was actually just trying to not push the audience away,

because they go well I'm not interested in a victorian pocket watch.

Just, I wanted it to look special.

I break everything but I did not break the alethiometer

'cause props were like if you break the alethiometer that is very expensive.

What do the symbols mean?

I absolutely love the set of my boat. So, everybody walks onto

that set and really wishes they could live there. On every shelf and every cupboard,

every cushion. I cannot tell you just the extraordinary microscopic attention to detail.

I will give you that.

I've just been doing a lot of scenes in the frozen waste of the north.

And then you walk into set and it's actually pretty stunning. And the light is

incredible. You are lit by our northern lights a lot of the time, so it's like being in a

brilliant, psychedelic disco sometimes. In a kind of frozen north sort of way.

I love the airships. They're really fun,

and we've had three different kinds of airships.

One that was like a tube, you know a london tube. One that's like a sort of private jet,

and one that's a military one. I mean they're amazing. I could spend all day in those.

The environments on this show are playgrounds really,

that are all different and stretch and pull on every muscle you have creatively.

I think I look at it from a kind of like 'how exciting is that?' perspective

rather than 'how terrifying is that?'

And it's such a fun challenge that

I'd defy anyone to not think it would be utterly brilliant thing to do. Why wouldn't it be?

It's one of the biggest challenges, I think. Because you could get it wrong, you could

so easily get it wrong and I'm desperately, desperately trying not to.