WHO is the most famous person you have interviewed? It is a question that journalists get asked a lot. Even after two decades in this gig, I am never quite sure how to answer. Firstly, define famous? Are we talking royalty, Hollywood status, longevity, global reach, meteoric rise, notoriety?

A better question would be: Who is the most fun to interview? Step forward Mark Bonnar who is a strong contender in that category.

Bonnar, 52, has rarely been idle in recent years, popping up everywhere from Line of Duty, Catastrophe and Shetland to Quiz, Apple Tree Yard, Unforgotten and the reboot of classic sitcom Porridge.

The Edinburgh-born actor is back on our screens this week as the darkly comic and Hitchcockian drama Guilt – the brainchild of Bob Servant creator Neil Forsyth – returns to BBC Scotland and BBC Two for a much-anticipated second series.

But what makes the man himself tick? Here, without further ado, we delve into the world according to Mark Bonnar. Buckle up …

The return of Guilt

When Guilt aired two years ago, it cemented itself among the realms of modern telly classics. The Herald’s TV critic Alison Rowat described the opening series as “the most impressive small screen debut since Tutti Frutti”. (And, believe me, she is a tough woman to impress).

The four-part thriller centred on brothers Max and Jake who, while arguing in the car on the way home from a wedding, accidentally run over and kill an elderly man on a dark road.

At Max’s ruthless insistence the chalk-and-cheese siblings – played by Bonnar and Jamie Sives – flee the scene, then set about trying to bury any evidence of their involvement. Inevitably, however, things unravel faster than they can tie up the loose ends.

“Max is a great character,” says Bonnar. “He is borderline sociopathic. The appeal is playing a character who maybe does and says things that we don’t think we could get away with in real life.”

Glasgow Times: Mark Bonnar during the filming of Guilt series two. Picture: BBCMark Bonnar during the filming of Guilt series two. Picture: BBC

As the first series of Guilt wrapped, Max had produced possibly the only selfless deed of his life and was poised to take the rap for their dastardly act.

What’s the situation now? Well … Max is in prison. Jake is in America. Their friend Kenny (Emun Elliott) is in sobriety and trying to build a new business venture. Roy – the gangland baddie – is still up to his old tricks (with Stuart Bowman replacing Bill Paterson who played the role in series one).

There are some new faces too: Sara Vickers, Greg McHugh, Phyllis Logan and Ian Pirie all join the series two cast. Throw in a couple of corpses, some murky goings-on, a few crossed wires and dubious characters aplenty, there is a tangled web being woven.

READ MORE: Bob Servant creator Neil Forsyth on writing new BBC drama Guilt

Will it keep us guessing? “Right to the very end,” confirms Bonnar. “To the last shot, basically. What you can expect is not more of the same, we are not knocking over and killing any other old people, but there are lots of new characters, which is exciting.

“The regulars are put in some rather tricky situations that they have to worm their way out of. Specifically, Max. But rather than running from and trying to avoid responsibility this time around, he is setting something up, shall we say? He has very different motivations.”

Glasgow Times: Mark Bonnar as Max in series two of Guilt. Picture: Robert Pereira Hind/BBCMark Bonnar as Max in series two of Guilt. Picture: Robert Pereira Hind/BBC

Is Max a changed man, then? “Through the course of the second series you learn a little bit more about him and find out he is not quite as out for number one as he used to be,” says Bonnar, cryptically. “Prison has changed him in some ways for the better and some ways maybe not …”

If Bonnar was to sum up series two of Guilt in a word: “Owls,” he says. Which is one of those answers where all will become clear very soon.

His Scottish roots

When we speak on a Tuesday afternoon in late September, Bonnar is somewhere around the corner from the Hertfordshire home he shares with his wife Lucy Gaskell and their two children. “We have just vacated our house so the builders can move in,” he explains.

His childhood took him to Scotland’s north-east coast and across the central belt. Bonnar was born in Edinburgh, then moved to Dundee where his father Stan, the environmental artist responsible for creating Glenrothes’s famed concrete hippo sculptures, was at art college.

(Quick aside: his father was also the creative brains behind East Kilbride’s landmark concrete elephants and Bonnar currently has a BBC Scotland documentary in the pipeline about the legacy of public art and sculpture in Scotland’s new towns).

Glasgow Times: Mark Bonnar returns to our screens in series two of BBC Scotland drama Guilt. Picture: PipMark Bonnar returns to our screens in series two of BBC Scotland drama Guilt. Picture: Pip

After living in Glenrothes, East Kilbride and Stonehouse in South Lanarkshire – a whistle-stop tour of new towns if you like – his family settled in Edinburgh in the early 1980s, where Bonnar attended Leith Academy.

Does he enjoy getting back to Scotland? “It is my home. I am very close to it in my heart,” says Bonnar. “But I am two sides of the coin because I have been down south longer than I lived up north which is a strange thing to think about. I have lived in England for a long time. And I love it.

“I love where I live now. London and the surrounds are a great place to be. It is a great part of the world. Divided loyalties. During the Euros it was divided loyalties as well.”

Filming on home turf

Bonnar has seen a fair bit of Scotland over the past few years. As well as filming Guilt, he is a regular on BBC Scotland drama Shetland – series six is set to air imminently – and is also among the cast for the forthcoming sci-fi thriller The Rig, shot largely in Edinburgh and due out on Amazon Prime Video next year.

Working on Guilt saw Bonnar revisit many familiar childhood haunts. There is a scene in the new series where Emun Elliott’s character Kenny is walking home to Pilton. Was that the famed “Banana Flats” aka Cables Wynd House, the architectural behemoth that dominates the skyline of Leith, I spied?

This prompts a fond chuckle and an affirmative from the actor. “It is always weird going back,” he says. “The school I went to, Leith Academy, is flats now and that is strange. The Banana Flats are an amazing location, an iconic piece of Edinburgh architecture which I believe are listed now.

Glasgow Times: Cables Wynd House, aka the famed "Banana Flats", in Leith. Picture: Gordon Terris/The HeraldCables Wynd House, aka the famed "Banana Flats", in Leith. Picture: Gordon Terris/The Herald

“It is not ‘Pilton’. That shot where Emun’s character walks home, for those who know – of which there will be a few – they will be going ‘That’s not Pilton!’. But it is great to get the Banana Flats in because they have been around since I was wee. They are such an Edinburgh monument.

“It is weird going to film in your old [childhood haunts], especially where you had most of your formative years – it is a strange experience. There are echoes and memories that jump back at you that you haven’t thought about for 40 years.”

There came further deja vu when he was working on The Rig. Set on the fictional Kinloch Bravo oil platform in the North Sea, the six-part series was made at Port of Leith earlier this year.

“Driving to set for The Rig, the route went right past my old secondary school. Every morning when I was going to work, I was passing Leithy and thinking: ‘Oh my God, there’s where Billy Gilfillan punched me in the mouth’ or whatever,” laughs Bonnar.

READ MORE: The Scots writer behind star-studded thriller The Rig being filmed in Edinburgh 

“It is a strange thing because your life is an ongoing wave of experience. You don’t often take time or indeed inhabit the places you used to inhabit for any length of time. So, when you do, and these things jump back at you, it gives you pause.”

Childhood aspirations

Let’s rewind a bit further. What did Bonnar want to be when he grew up? “It changed as the years went by,” he says. “The first serious stab I had at ‘this is what I am going to do’ was when I was about 11 and in first year at Leith Academy.

“In history we studied the bog man. Do you remember the bog man? I was absolutely fascinated by this. When something brings the past into sharp focus as a child it creates an indelible impression. As you can tell because I am still speaking to you about it now.

“That photograph with his whiskers still on his chin, the fingerprints still on his fingers and the teeth still in his mouth. The eyes closed like he was asleep, albeit he was soaked head-to-toe in peat. It was fascinating.

“At that moment I decided I wanted to be a historian. That maybe lasted for a couple of weeks. Then it went by the wayside.

“But, as with many things in my psyche, it is all ships in the night. Which is why acting is the perfect job for me. I get intensely interested in something for a very short period of time and then move on.”

Glasgow Times: Mark Bonnar with Guilt co-star Emun Elliott who plays Kenny. Picture: Robert Pereira Hind/BBCMark Bonnar with Guilt co-star Emun Elliott who plays Kenny. Picture: Robert Pereira Hind/BBC

Successes and missed opportunities

Bonnar’s all-time favourite acting role? “Whatever the next one is,” he says. “There are no missed opportunities. Well, there are hundreds and thousands of them but what is the point in visiting that? Move on. If you learn anything as an actor, it is when to say no and don’t dwell on the past.”

The living person he most admires

“My wife,” says Bonnar, without hesitation. “Why? She is a remarkable human being and her ability for empathy and compassion knows no bounds. She is resourceful, witty and wise. All the things that I wish I was.

“But luckily, I am with her, so at least I can glean a little bit hopefully as we proceed through life. We have been married for 14 years this December and together for about 18 years.”

Top of the bucket list

“I want a campervan,” he proclaims. “Especially in the current climate where nobody is particularly bothered about going abroad – well, we aren’t.

“I want to take the kids to the places I went on holiday, up the west coast of Scotland and to Torridon and Glen Etive and the Cairngorms National Park. All those wonderful places and others I haven’t been to before.

READ MORE: Castaway returns: Ben Fogle on his new TV series celebrating Scotland's islands

“There is no other country in the world that looks like Scotland. When you are standing in Glen Coe, it gives you something and it takes something away. You feel the history. I want my kids, who are six and 10, to experience it and I want us to do that in a campervan.”

If he could meet anyone from history

“Laurel and Hardy,” says Bonnar. What would he talk to them about? “Oh, I don’t think I would say anything. It is that dinner party guest question, isn’t it? I would quietly eat my toast and smile at them every now and again. And just be in their company.

“They were a shining light of my childhood and one of the earliest memories I have. It was always duos for me: Tom and Jerry, Laurel and Hardy, Morecambe and Wise, The Two Ronnies.

Glasgow Times: Laurel and HardyLaurel and Hardy

“Laurel and Hardy engendered not only hysteria as far as laughing was concerned – I would cry laughing at some of their stuff – but also, they engendered an empathy because, despite their huge and many faults, they were totally and utterly loveable.

“I believe they were like that in real life. I read a biography about them many years ago when I was still quite young and that made an impression on me. I love them.”

Analogue dreams

Vinyl or streaming? “I am lucky enough to have a fairly nice turntable,” says Bonnar. “When you put on an LP and everything is working and there is no buzz from the turntable – which I have at the moment and it is a pain in the a*** – there is nothing like that sound, it totally envelops you.”

Move over, Superman

If Bonnar could have any superpower, what would it be? “The ability to grow my hair at the drop of a hat,” he says. “If I needed long hair for a part, then I would quickly grow some. I could quickly fill in the baldy patches or choose to have baldy patches if I wished …”

Glasgow Times: Mark Bonnar as Max in series two of Guilt. Picture: Robert Pereira Hind/BBCMark Bonnar as Max in series two of Guilt. Picture: Robert Pereira Hind/BBC

Lessons in good and bad advice

His trusty motto? “Try not to be a s***,” deadpans Bonnar. “I would like to point out I don’t always succeed – that is where the ‘try’ part comes in.”

What about the best and worst advice he’s been given? “Again, that would be ‘try not to be a s***’. Well, it wasn’t quite as polite as that. Somebody once said to me and it appealed to me at the time, although I don’t really drink or smoke anymore.

“It was: ‘Don’t be a c*** and get good gear.’ I appreciated that as a life lesson when I was in my mid-thirties. But I don’t drink anymore. I would withhold on that as advice, though, because ‘get good gear’ isn’t good advice.”

Life-affirming films, theatre and literature

“I am, as are we all, the sum of my parts,” says Bonnar. “And all those parts are films, books and scripts I have read and things that have moved me.

“My school friend Andy Nicol did an amateur production of Hair years ago. I was auditioning for drama school at the time and just starting to dip my toe in the water. He did Hair at the Millfield Theatre in Enfield. That deeply affected me in an eyes-wide-open and full-of-wonder way.

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“In the same way that Cyrano de Bergerac with Gerard Depardieu affected me. Things that fill you full of wonder are worth seeking out because that is a great thing to feel.

“I love horror films and stuff that makes me uneasy – I have always been attracted to that – but things that fill you full of wonder are worthwhile to seek out. Life-affirming stuff is worth its weight in gold.

“Books like The Catcher in the Rye. That is one of my favourites. Franny and Zooey is another one of JD Salinger’s and a fantastic book. How long have you got? I am 52. I have seen a lot.”

Glasgow Times: Mark Bonnar returns to our screens in series two of BBC Scotland drama Guilt. Picture: PipMark Bonnar returns to our screens in series two of BBC Scotland drama Guilt. Picture: Pip

Burning ambitions

What is his ultimate goal or ambition? “The ultimate goal would be to score against Real Madrid,” he says, laughing. “I am happy to be working. I would love that to continue. I love my work and feel like I am nowhere near where I should be with it sometimes.

“It is a hackneyed old phrase ‘imposter syndrome’ but you sometimes feel ‘why am I doing this?’. I would love to get to a place where I know why I am doing it. I do know that I am alright at it – I don’t wish to appear falsely modest – but we always doubt ourselves, don’t we?

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“It would be nice to get to a place where that isn’t quite such a big part of my daily routine.”

Guilt returns to BBC Scotland on Tuesday, 10pm, and BBC Two from Thursday, 9pm. All four episodes are on BBC iPlayer from Tuesday evening