Read on to find out more about Jay, why he liked filming the '60s scenes, and, um, light switches...
> White Heat Claire Foy, Sam Claflin Q&A: 'It's an emotional journey'
Can you give us a quick overview of what White Heat is about?
"It's about a group of friends - or people who seem to be friends! - that meet in 1965. They all move into a flat together and then proceed to live out their lives in one way or another, involved with each other."
You're playing Jay - what can you tell us about him?
"When you meet him he's this 19-year-old, wet behind the ears, gentle kind of guy from Solihull in Birmingham, and you soon find out that he's gay and he's living with this secret, confined in this flat. And career-wise and study-wise he's an aspiring paediatric surgeon."
Do we see him become a doctor?
"Yep, you see him become a doctor, without giving too much away. But that's a small part of his storyline, really - I guess the main crux of it is him dealing with and living with his sexuality, his sexual orientation."
How does Jay get on with the other characters?
"He gets along with everybody, he's a really lovely guy! He hasn't got any bitterness or vendettas towards anybody - his only struggle is with himself throughout the whole thing, really. He obviously disagrees with certain things that people do but he's so non-judgemental.
"He's always there to lend a hand whether it's in terms of by helping flatmates out or just allowing them to confide in him or anything like that. However, he is closer to Orla than everybody else, because she knows more or less the full extent of his situation and what he's going through and they confide in each other, so he does have this special relationship with Orla."
How does Jay change as the series goes on?
"In the very beginning, he literally comes straight out of his family home down to London - moving to university is scary now, but back then it was like moving country! He starts off pretty much as his dad - he's wearing the tie and the watch and the cardigans that he would have seen his dad and his grandfather wear as he was growing up. So he's this square, naive, wet behind the ears guy who's harbouring a secret.
"And then there's this explosion two years later in '67 when he's been in the house for two years, when you see him all of a sudden wearing tie dye, leather jackets - he's got a bit of a swagger about him, he's exploring what it is to be himself. So in the first two years, in the first episode, there's a vast change in him, but there are a thousand others that happen throughout the rest of the 40 years that we span!"
What's your favourite decade to film?
"I think probably the '60s, just for a couple of reasons. It's further away from what I know, further back, so it's more alien and more exciting. And I think it was just such an explosive time in general and there are a couple of party scenes that we have and you think, 'God, the parties were so much cooler back then'. So I like the '60s and the costumes and stuff."
I was going to ask you about the costumes - has there been anything that you thought, 'Oh God, I can't believe I have to wear that...'?
"There have been one or two things. We're not made to wear anything - they'll respect it if we say, 'Look, I really don't think he would wear that'. However, what I've learnt is that the thing that you're most repulsed by early on ends up being the thing usually that makes your character, because it forces you to change the way you look at something and adopt the way the character would see it. I think I'd be reluctant to shun anything straight away.
"For example, a couple of days ago I did my first '80s scene, and lo and behold there was a big, pink jumper hanging up as I walked into my trailer! And I thought, 'You know what, it's good for him to have a bit of colour', and this is a stage in the story where I think he would wear a bit of colour. But you'd never see me walking down the street in a pink jumper, ever! So it's quite funny - it's quite fun to step into the characters' shoes and leave yourself at the door."
What attracted you to the show?
"He's a challenge. I'm a straight guy and the thought of playing a gay guy is exciting because it's a challenge. I want gay people to watch this and from a purely selfish perspective, if they're looking at Jay and believing that he's in that situation and identify with him in some respect... That for me was a challenge because it's one thing acting something, but it's another acting something that's believable and real.
"And whether I've done it, I don't know, but that was definitely something that attracted me to it. And the script, the colour of the script - all the different trends in it, and Paula [Milne]'s writing is amazing. It's really, really good - there's so many different levels and layers and bits of nostalgia. It's great."
Why do you think people should tune in?
"It's just something different. I don't think I've seen anything like this. Any Human Heart I guess is the closest I can marry anything up to the ageing area of it, but that was only about one character - this is about seven different people. There's going to be a character in there for everybody that you can empathise with or identify with.
"And it spans across the last 50 years - those 50 years inform everything about our lives today. Holding an iPhone... you'll see what happened back then before they had phones, when they got phones, how big they were. The light switches changing! I walked on set the other day and I noticed the light switch had changed from one of those round ones to one of those square ones, and I thought, 'Well, yeah!' As long as I've lived, they've always been square, but of course they change.
"There's so much detail in there for everybody. I think a young audience will look at it and go, 'Wow, is that what happened before I was born?' And an older audience will sit there and go, 'Yeah, I remember that, I remember that' and get so much out of the work we've put into it, hopefully."
White Heat airs on Thursday, March 8 at 9pm on BBC Two.