When I say Great Expectations, what are the first images that come into your head?
It’s kind of cheeky to say it because I'm playing Magwitch but it's the graveyard scene from the original movie. That haunting image. And Miss Havisham as well. The haunting image of this old lady who’s been jilted and resentful. That’s a powerful image.

How does this differ from previous versions of Great Expectations?

I think the casting is inspired. I was excited when I heard Ashley was going to be playing Jaggers – he’s mastered language as a rapper and is an incredible actor. As an actor you'd be lying if you didn't say that you're always intrigued as to who’s going to be the other cast members! I’m a massive fan of Olivia. It just works. When they said Olivia was going to play Miss Havisham I was like: they’ve nailed that. Sometimes adaptations can be a bit dusty and old, but I think Steven's was unashamedly modern.

Can you tell us a bit about Magwitch?

It's hard to describe him really because he goes on a journey. It depends which Magwitch you're talking about, you know, he's quite different at the beginning to the end. Magwitch is a troubled man. On the surface, he's a convict, a rogue, a highwayman, a legend of the road, and he's lived the life of sin. We meet him when the repercussions of that are in full swing. Then there’s an awakening, and from there on he's someone who is trying to do the right thing in life.

How much of a thrill has it been to put your stamp on such an iconic character?

It’s humbling, there's no doubt about it. I'm from the Elephant and Castle, that's where I grew up and where I live now, and it's where this is all set. There was a great line in one of the earlier drafts, where Jaggers sends Pip off to South London and says, "Take this letter to the Walworth Road." Pip says, "What if anyone stops me?" And he says, "Don't talk to anyone within two miles of the Elephant and Castle, they're not to be trusted," and I just laughed. That's where I'm from, I live on the Walworth Road. I really wanted to tell, for what it's worth, my interpretation of who Magwitch is.

You said you had to lose weight for the role?

Yes, we were laughing when I took the role on! I was quite overweight and there was potentially a naked scene where we'd see Magwitch's body, and he's very strong and hungry – famished – on the run in shackles and he hasn't eaten, so I needed to lose weight for sure, and ideally I would have put some muscle on as well. I lost 22 lbs – it's a lot of weight to lose. I didn't know I had that on me if I'm honest, but it came off, and so to do that it was a very strict diet. It's not easy, at my age, I love my puddings and desserts. So the diet finished and I said I never want to see another piece of broccoli again. And then we came to Pinewood Studios, in the water tank, and to make it look like the Thames, they put like a silt in it and fill it with broken broccoli. I probably ate more broccoli that day than in the previous four month of the shoots! So now I officially don't ever want to see another piece of broccoli as long as I live. I'm done with that stuff.

What was it like working with Olivia Colman?

Olivia's incredible. I came off Twitter because of Olivia Colman. Maybe I shouldn't tell this story but she gave a performance in a film called Tyrannosaur that is up there with the greatest performances of all time by anyone, anywhere, ever, and she didn't get a BAFTA nomination. I'd always promised myself that I would never get political on Twitter, and all of a sudden I'm publicly declaring, that they should be ashamed of themselves for not nominating this performance. And then I thought, I've got to come off it. So Olivia Colman is the reason I came off Twitter. I'd never met her, I was just kind of outraged at her not getting nominated for that performance.

But anyway, I digress. Look, it's Olivia Colman. I could have acted with her all year and I would never have got bored. I think she's lovely and she's a beautiful soul as well, a very kind woman. The first day I worked with her, I'm not saying this for the purpose of the cameras, I've told a few people this, but I bounced out of bed the next day. I couldn't wait to get in and start work with her, and that's a lovely thing to happen.