"There were people selling stuff out of bags. I’m not talking heroin. I’m talking macaroon bars." Unforgotten's Mark Bonnar on growing up in Leith

We will probably never know. Because at 48, and with more than 20 years’ experience behind him, Bonnar has proven himself more than all right at the acting game. Soon he will be back on Channel 4 in the third series of Sharon Horgan and Rob Delaney’s funny, frank and really rather filthy sitcom Catastrophe and right now you can see him on the third channel playing a gay barrister in ITV’s perfectly entertaining meat-and-potatoes crime drama Unforgotten, alongside Sanjeev Bhaskar and Nicola Walker.

In fact the latter is a good excuse to further probe the gap (or lack of it) between real life and the acting life. So, for anyone who watched the first episode of Unforgotten on Thursday night let it be known that in the real world Bonnar has never actually keyed a car before.

“Does it look good?” he asks. He hasn’t seen the episode when we speak. “I’m glad it does. I wanted it to have the correct level of vehemence.”

OK, that’s sorted. But tell me, Mark, have you ever kissed a man before in real life? “Yeah, loads. Hasn’t everyone? That is surely part of your journey as a man,” he says, smiling.

Bonnar is quite frankly a silver fox of a man who has retained his Scottish accent despite living in London and its surroundings for a couple of decades (“a lot of my friends who’ve come down have kind of lost their accents but that’s my bread and butter so I try not to let it go”). He has travelled in today (it’s lateish December) from Hertfordshire where he lives with his wife and fellow actor Lucy Gaskell, their daughter Martha and son Samuel, who will turn two in March, to talk about acting and ambition and his days at Leith Academy.

If I’m honest I mostly wanted to speak to him today because of Catastrophe. Huge fan. So, it turns out, is he.

Bonnar plays Chris, the chain-vaping, potty-mouthed best mate of Delaney who was married to Ashley Jensen in the first season and was hanging around outside clubs for transgender sex workers in the second. In a show full of great lines Bonnar gets some of the most shocking.

Does he ever read the script and think: “I can’t say that”?

“No. Usually I go, ‘You beauty.’ Some of the one-liners are great. It’s a real joy to do.

“If I wasn’t in Catastrophe I would be a fan anyway. I think it’s just a wonderful, wonderful piece of work. I’m blessed to part of that show.”

(When we speak it’s before Carrie Fisher’s tragic death. He will later post on Twitter that working with her on the sitcom left an indelible impression. “Warm, wise and bloody funny.”)

Presumably Bonnar feels he’s got this acting thing nailed now. You’ve arrived, Mark, haven’t you?

Hmm. He’s not so sure. “I’m always worried about where the next job’s coming from. Everybody’s always worried about where the next job’s coming from. I’m certainly very happy to have done the work I’ve done over the last few years. But I think if you start to go, ‘Yeah, I’m doing all right,’ that way danger lies. That’s exactly when you stop being vital and hungry and ambitious.

“I was just saying to the driver today I’ve had two whole years, two separate whole years, of unemployment. I started doing the job in 1996 and I did theatre pretty much for 10 years. I had a bit of radio and some voiceover stuff that kept the wolf from the door, just.

“Paradox [a BBC sci-fi cop show starring Tamzin Outhwaite in 2009] was one of the first big parts I had on telly and after it finished I thought: ‘Right, OK, let’s see what happens now.’ And nothing happened for nine months. I redecorated the living room. I did all kinds of DIY around the house and twiddled my thumbs and went a bit mental. So yeah, it can happen at any time. You never rest on your laurels.”

Well, maybe. At least after 20 years he must know he’s quite good at what he does. When did he first realise as much? “Probably November. I don’t know. I’m still pulling it off by the skin of my teeth.”

Mark Bonnar tells me he grew up “all over” Scotland. Well, the central belt anyway. He was born at the Western General in Edinburgh then moved to Dundee where his dad was at art college. He thinks he might have been there for about three years or so. “There’s certainly pictures of me the same size as my son is now being fed a bottle beside a massive Newcastle Brown ashtray filled with douts right beside my head.”

ou started smoking early then? “Yeah,” he laughs, putting on a gruff voice, “I’m ready for my milk now, Mum.”

After Dundee the family moved to Glenrothes and then East Kilbride and Stonehouse, South Lanarkshire. A tour of Scotland’s new towns, basically. “We moved around so much because my dad was an artist. He still is an artist and at the time back in the good old 1970s councils used to employ artists to spruce up the horrific new towns that they’d thrown up all over the place. So he used to make the s*** look better. Which he did. He’s wonderful. But that’s why we dotted around.

“I know a lot of actors have that dotting-around thing in common. You arrive in a new place and you have to quickly assimilate yourself by whatever means.”

After Stonehouse, the family moved back to Edinburgh. “I arrived at Leith Academy talking like a weegie,” he says. It didn’t last. Assimilation. He was at Leith for the first five years of the 1980s. The Trainspotting years, essentially. “It was the heroin capital of Europe when I was at school,” Bonnar agrees. “But I didn’t get involved in any of that. I had my pals at school and people you had to watch out for. But that’s school. There were people selling stuff out of bags. I’m not talking heroin. I’m talking macaroon bars. Far more dangerous if you owe them money, which I found out.”

Macaroon debt aside, he enjoyed his time there. “Those were my formative years. I discovered smoking and drinking. I started smoking at 14-ish. My best friend then, Keith, is still my best friend.”

At home he lived with his parents and younger brother Vinnie. What was his role in the family, I ask. “Big brother?” he suggests tentatively. “I don’t know what my role in the family was. My adopted role was arsing about. It’s painful to look at now I do it for a job. Photographs from when I was maybe 10 to 15 were pretty much me making some kind of face.

“It’s so long ago now,” he adds, before returning to the question. “Big brother and hopefully not useless son.”

Hmm. Does he really see acting as “arsing about”, I have to ask. “No,” he admits. “We tend to make light of it.”

Well, is he embarrassed at all by what he does? “No, it’s a real job. The self-deprecating side of it comes from the fact it’s kind of hard to pin down what you do.”

He goes off on a riff about acting’s unpindownability. “Paul Scofield wrote a brilliant letter to Richard Eyre when Eyre asked him to come and talk to some students about his process, saying essentially that the more an actor talks about acting the more boring it becomes.

“It’s impossible to describe what it is. You can describe the nuts and bolts of it but that’s boring as well. You might as well ask a cabinet maker to describe what gauge of screwdriver he used to put in those kinds of screws and what kind of glue he uses. It’s hopefully a beautiful thing to look at but the process to get to that place isn’t essentially that exciting and it doesn’t enlighten much in any way. Or make for good copy.”

Well, he says that, although right now, I tell him, I’m thinking there’s a really good BBC Four documentary to be made about a cabinet maker talking screws and glue.

He laughs. “There’s an ethereal side to the job which happens between reading something, it festering in your brain and you trying to inhabit it. I guess that’s why a lot of actors are like: ‘It’s just a silly job, isn’t it?’ You can’t put your hands on what you do. You do it and hopefully people like it.”

In a parallel universe Bonnar is still working for Edinburgh City Council, possibly in the planning department. He left school at 16 with no particular direction in mind. He’d won a school drama prize when he was 12 but was actively discouraged from drama school by a careers advisor, and spent his teens and early twenties dotting around on the jobs front. He was a salesman, worked in a library, even applied for a job as a mortuary technician (“Thank Christ I didn’t get that”). He then got a job in the council planning department, stayed there for a couple of years, even got a promotion. At the time it would have been seen as a job for life. But not his life as it turned out.

“I think in any aspect of my life there is that restlessness,” he admits, “which is why this [acting] is the perfect job, because jobs themselves only last for three months and then you’re on to something new.”

While working for the council he was doing that “arsing about” thing around the office and a couple of his colleagues, who were involved in amateur theatre in Leith, suggested he transpose it to the stage. “I wasn’t thinking about it. I hadn’t thought about it since school. I watched films and TV without thinking, ‘That’s a job.’”

After three or four amateur shows, however, someone suggested he apply for drama school.

“And I’d just bought a house so that was a big plunge. I decided to do a one-year course at Telford just to see if I was any good at it and from there I applied to drama school proper and went to Glasgow [to attend the former RSAMD to be precise] and rented my house out.”

Before we leave Edinburgh though, Mark, here’s your chance to confess. About those couple of years in the planning department. You can now tell us. Which egregious example of bad urban planning were you responsible for? Is there a superfluous traffic island you approved? A pointless sign? A dreadful office building?

“There’s an awful block of flats … No, I was just a technician. ‘It was nothing to do with me, guvnor.’ I checked applications. I liaised with architects. I made sure that everything was technically in order before passing it on to a planner. I didn’t take any backhanders...”

He met his wife Lucy when they were both in a production of The Cherry Orchard that Dominic Drumgoole was directing. She was playing Dunyasha and he was Trofimov. “We didn’t have anything to say to each other onstage but obviously had a lot to say to each other offstage.”

Their daughter Martha was born 10 years later when Bonnar was in The Cherry Orchard again, this time at the National. He was Trofimov that time around too, “playing a 30-year-old when I was 42. I had a wig, obviously. It holds a special place in our hearts, that play.”

I think he’s probably sold on this acting lark now. The police force’s loss and all that. You do wonder, though, if he’d started later would he have got to where he is. Where does he stand on the Cumberbatchification of the acting classes these days? Is it harder than ever to break into the profession if you’re from the working class?

“Having the knowledge that you will be thousands of pounds in debt by the time you finish any course is bound to be off-putting for people from certain backgrounds. There are ways and means, but it’s probably harder now. So I would say sad but true, maybe.”

He looks up and out. “Great view,” he says. True. From up here you can see London spread out before you. This is his world now. Accent apart, how, I wonder, does his Scottishness still manifest itself? Is Irn-Bru on tap in his house? Is it square sausage for breakfast every day?

“I wish. Have you tried getting square sausage in London? I get haggis whenever I can. I love haggis.

“Does it manifest itself in food?” he asks himself. “People, when they learn you’re Scottish, say: ‘Have you had a deep-fried Mars bar?’ That’s Scotland’s legacy.”

And has he? “I have but as I always say it was in a brasserie in Fulham.”

Unforgotten continues on STV on Thursdays at 9pm