If the acting ever dries up, then at least Nick Frost has a plan. “Burgers,” he says, without a pause. “Me and my mate Danny have been talking about this a lot – finding one of those places in a nice park, you know where there used to be a parkie’s hut, but now you can get a decent bacon roll and a cup of coffee? I imagine doing that, but with cheeseburgers: shit mince, onions, American cheese, done.”

It’s a career path he appears to have thought about rather a lot for an established Hollywood actor. I can’t imagine, say, Martin Freeman has an alternative life as a barista mapped out. But then Frost has his reasons for worrying. As a teenager, his father’s furniture business collapsed pretty much overnight, leaving the Frost family broke, homeless and emotionally devastated.

“And that does still play on my mind,” he says. “I think about people during the 90s stand-up boom who were massive, and you think: ‘Fucking hell, what happened to them? How do they make money? How do they support their families?’ I might have a beautiful life at the moment, but if things didn’t come in for a year…”

He places a hand on his chest. “I can feel my heart beating now just thinking about it,’” he says. As it turns out during this interview, there are a few things from Frost’s past that he’s still trying to shake.

Hello, grappling fans: on the set of Fighting With My Family with (from left) actor Lena Headey and director Stephen Merchant. Photograph: Robert Viglasky/AP

But for now, shit mince is off the menu. He’s currently holed up in the offices of Stolen Picture, the production company he set up with his best buddy Simon Pegg in 2016 – ostensibly to take ownership of the films and TV they make, but secretly to give the pair an excuse to hang out together again, like how they used to before they made Spaced, the cult sitcom that launched their careers. Frost – so often portrayed in his films as a layabout – likes to get into the office early, around 7am when there’s “no traffic and I can take my jeans off”. He’s not entirely joking. Today he’s redefining the meaning of office casual – Ellesse T-shirt, shorts, two chains and some impressively meaty gold rings.

He’s here to promote Fighting With My Family – a wrestling comedy based on the real-life story of Saraya-Jade Bevis, a working class Norwich teenager from a family of wrestlers who, under her stage name Paige, becomes a World Wrestling Entertainment champion by the age of 21. Directed by Stephen Merchant, and boasting an impressive cast – Florence Pugh, Jack Lowden, the Rock – it manages to document the glitzy WWE world without losing its cheeky British humour.

Frost was already a fan of the 2012 documentary that the film is based on, but what really drew him in was his connection to his character, Paige’s dad Ricky – a former inmate driven to be a good man to his family. “Being a dad now, I get him,” he says. “He shows that you can be bad and find love and redemption, and still be a good dad.” Paige’s family reminded Frost of his own – loud, lairy, loving – and he says shooting the movie was the most fun he’s ever had on set. For the fight scenes, the cast spent two weeks at the glamorous location of Hornsey town hall in north London, as a team of wrestlers slammed them around. “It looks like an explosion of violence onscreen, but when you’re in a tight hug they’re actually whispering, ‘OK so I’m going to put you down now,’” says Frost. “There are lots of little things to learn to stop yourself getting hurt. Although Jack put a lot of weight on – I had to catch him tonnes of times and it was like: ‘Oh shitting hell, you’re so big now!’”

Fighting wasn’t unheard of in the Frost family. His autobiography, Truths, Half Truths and Little White Lies, recounts his mum seeing off the school bully, and then the bully’s mum. Frost, meanwhile, is teaching his son Mac to kickbox – “He’s seven, he can feel a rage building inside him, the testosterone. Although if someone hit him back on the chin he’d be like, ‘Mummy!’”

‘We were affectionate. We were in love. It was a platonic, non-sexual love affair, for 25 years’: Frost with Simon Pegg. Photograph: Richard Saker/The Observer

Frost has talked before about how fatherhood came at the right time for him, when his spirit was at a low point and he needed direction in life. In 2015 he divorced Mac’s mother Christina, but the pair remain close and share parental duties. Four months ago, Frost became a father for the second time, and says that he and his girlfriend have forged a bond with Christina that ensures the kids will all be happy. “It isn’t easy, but it works,” he says. “I think when Chris and I got divorced we knew people who didn’t [get along] and you see what it does to their kids. I get sometimes that there’s no other option, but once you’ve made the choice to get divorced for the benefit of the child, it seems churlish to then be shit to each other.”

He doesn’t like to talk about Chris too much, for fear of upsetting the delicate balance they’ve worked on – although he does mention that she got “really mad” when he published his autobiography. “Yeah, she thought it was really personal.”

It would be hard to argue with that assessment. Truths, Half Truths and White Lies delves into the drinking problem that ultimately killed his mother, his own struggles with addiction, his battles with depression – even a suicide attempt. There’s joy and laughter, too, but when it comes to the dark side he doesn’t hold anything back. Perhaps surprisingly, the book doesn’t end with a happy resolution – fame hasn’t healed him, and neither has fatherhood entirely.

“And that’s the same now,” he says, giving his beard a tug – tricky subject terrain can be measured by the amount of beard that gets tugged. “I don’t think I’ll ever be right, I don’t think I’ll ever be ‘fixed’. It’s a case of patching up a sinking ship. That sounds creepy and dark. But it’s hard. Life is fucking difficult.”

Frost report: with the cast of Spaced. From left: Nick Frost, Simon Pegg, Jessica Stevenson and Mark Heap. Photograph: E4

Frost grew up feeling like he’d lost his family – his mother to drink, his dad was never the same after his business collapsed. But through meeting Pegg – and the gang of slightly unhinged comedians around him – he built a replacement family. Frost and Pegg became thick as thieves and their creative partnership blossomed into a string of hit movies: Shaun of the Dead, Hot Fuzz, Paul. Nowadays, though, with Pegg living out in the country, their friendship often has to rely on Skype calls and “texting each other 10 times a day”.

Earlier this year, I interviewed Pegg, and he described his years struggling with alcoholism as the pair’s fame grew. “I hid it,” he told me. “I hid it from Nick as well. One thing [addiction] does is make you clever at not giving anything away.”

“Well he tried to hide it,” says Frost, today.

You didn’t buy it?

“No, of course not. My mum and my sister and my brothers were terrible drinkers. You can’t kid a kidder.”

Watching his best friend struggle was tough, says Frost. He tried to do what best friends should do. “Although in hindsight I could have flagged it up more or helped him more,” he says. “But at the time, you kid yourself that the worst thing that could happen isn’t going to happen, you know? It’ll be fine. And then you get to a point where it’s not fine, at all… so when do you step in?”

Did he step in?

“Eventually we all jumped in and got involved to save someone, to save our mate… and that probably goes back to us choosing [each other] as our family.”

There’s something quite strange, and very male, about two friends – so close that they once famously shared a single bed together for nine months – who were simultaneously struggling with these demons and not talking to each other about it. They even made a film together, World’s End that, in retrospect, seems to directly reference their struggles.

Back from the dead: Shaun of the Dead (2004) with Frost, Pegg and Kate Ashfield. Photograph: Allstar

“Again, it’s that thing of not wanting the party to end,” says Frost, tugging on the beard again. “It’s cool. And when it isn’t cool any more, you’re not sure what to do.”

Frost exhales. It’s not that he’s against talking about any of this, more that he seems still to be getting his head around it. “It’s complicated,” he says. “With my mum, for years I couldn’t look at her, it went past ‘I love you’ to ‘I love you so much that I can’t look at you.’ Now, I think: ‘Could I have helped my mum more?’ But that chance has gone. So I try not to beat myself up in terms of that.”

Frost no longer drinks. In fact, the Sunday after our interview marks a full year since he last touched a drop. How does that feel?

“All right,” he says. “There are lots of nice non-alcoholic beers on the market now, so I can still sit in pubs with friends, which is nice. I wish they’d do them on tap though, because it costs £8.40 for two bottles of Bitburger to pour into a pint glass. That’s annoying.”

Given the bond between Pegg and Frost, and the fact that the latter was dragged by the former somewhat reluctantly into the world of acting in the first place, you might imagine that he still feels a little lost when it comes to making a film without his buddy beside him. But no. “I think it’s probably scarier with him in it,” he says. “We had a fantastic chemistry and that’s still the case. But in terms of wanting to do a good body of work, I’m happy to not do... it’s better for me as a performer.”

Friday night takeaway: with Lena Headey in Fighting With My Family. Photograph: Robert Viglasky/AP

The story of Frost and Pegg sharing a bed is well-trodden, but I have to admit to being struck by the way Frost described it so tenderly in his autobiography: “We’d sit up in bed and read a big book together, usually a glossy atlas or a book about Christmas,” he wrote. “He’d hold one page and I’d hold the other. It was cold at night and we’d just snuggle down and sleep. It felt right.”

It’s almost as if their relationship was more suited to 2019, where masculinity is being redefined and detoxified. Actually, says Frost: “I think we probably started all of that.”

Really?

“Yeah. In terms of groups of men watching films that we made and then reading about the people in them sharing a bed together. I’m sure they were like, ‘If they can fucking do it, then we can, too!’

“I hadn’t seen many people before doing that,” he continues. “You were either gay or straight. There was never that... we kiss on the mouth, yet we’re heterosexual. We were affectionate. We were in love. It was a platonic, non-sexual love affair, for 25 years. So in terms of whoever seeing that – fucking Loaded magazine and Nuts and Zoo – and realising you can have a girlfriend and still kiss your best mate on the lips, yeah.”

If Stolen Picture really was a front to allow the pair to spend more time together, then it’s working. They’re currently holed up in their central London office, tasked with writing eight episodes of their new horror-comedy television series, Truth Seekers, in six weeks. The series follows a three-person paranormal investigations team, and will be partly informed by the trips to haunted locations he and Pegg used to take back in their pre-fame days. “The shitter side of ghost hunting,” grins Frost.

He has other projects on the go, too: he’s 50,000 words into a sci-fi novel, although he concedes that publishers haven’t been beating down his doors to secure the rights. He’s also signed up to play the lead in a Captain Pugwash movie, which he’s keen to make happen. “I’ve realised in this industry that you’ve just got to keep on going,” he says.

In the production notes for Fighting With My Family, Frost is described as a “comedy veteran”. It’s undoubtedly true. But in some ways it is as if he’s wandered into showbiz by accident and just happens to be good at it. He still seems like a newcomer – and that is part of his charm.

Frost gets his phone out and says: “Look what Simon found yesterday.” On the phone is a picture of a VHS tape with “Nick’s first gig, Cosmic Comedy Club, 1994” written on it. “Simon sent me this yesterday and said, ‘You’ve been in showbiz for 25 years!’” He pauses to take that in. “I can’t remember the point in my career where I started playing people’s fathers. And not babies, but, like, 25-year-olds.”

As we wrap up the interview, Frost looks a little distracted by something, although I’m not sure why. Was it the existential crisis brought on by the videotape? Or something else that we’ve covered? A few days later he gets in touch. He wants to make sure his thoughts on drinking are made clear, so he sends over a brief statement via email: “I think I recognised something in myself which could have, in the end, led me to have my own problems. I made the decision before I got to that point to stop. It just isn’t worth it. I watched lots of people change and die because of drink and I didn’t want to be one of them.”

He may be a troubled work in progress, patching up the holes in the ship as he goes. But he’s still afloat, and I suspect the world may have to wait some time to try that Nick Frost cheeseburger.

Fighting With My Family is in cinemas now