Only true fans of UK actor will remember him in this role

What's not to love about a fictional detective with a quirky trademark? Think Morse with his crosswords and love of classical music, Poirot with his marrow growing and moustache maintenance, and Columbo who loved cooking chilli and tinkering with his old Peugeot.

Yet none compare with Alex Ridley, the copper who croons at a jazz club when he's off duty. And what a voice the retired detective inspector has - or rather the actor Adrian Dunbar, 67, who plays him.

But those with long memories will know this already. In 1991, Adrian starred as real life Irish tenor in the musical comedy drama film, Here My Song.

"I've been interested in music all my life," smiles Adrian, who hails from the town of Enniskillen in Northern Ireland, as we chat over Zoom. "I formed a country music band with friends back in the 1970s, was even an Elvis impersonator for a while and have played in many bands since. I used to play bass guitar but I just sing now.

He continues: "It was a bit of a gamble incorporating a musical element into a serious police drama - especially when you consider that a huge part of Ridley's back story is that he lost his wife and daughter in a fire. But it works.

"The songs, written by fantastic singer/song writer Richard Hawley, are really about male grief. They suit Ridley's character and what he's going through. Music brings him a certain solace. We're able to meld the songs into a kind of subtle comment about what's happening in each episode. They're a kind of reflection."

What also happens in every episode of this second series - without fail - is that Ridley wears the same battered, black leather jacket he donned constantly throughout the first. A signature piece of clothing is another character-defining device much loved by writers of crime fiction - from Vera and her unbecoming bucket hat to The Killing's Sarah Lund's Scandi-style Faroese jumper and Sherlock Holmes' iconic deerstalker hat. Adrian laughs in a it's-a-fair-cop kind of way when questioned about it.

"Well done on picking that up but, er, it's a brown jacket, actually," he jokes. "It's police procedure so I really must pick you up on these details! But yeah, we did want to find an item of clothing that would be associated with Ridley.

"We found this particularly beaten-up old jacket and thought it would be perfect to add characterisation. As an actor, putting it on is a great help, too. When I wear it, I immediately feel like him."

There is a moment in the series when Ridley sees a girl he's convinced is his daughter. "The grief runs so deep," says Adrian. "It's a difficult thing to deal with psychologically but it's interesting and I think we handle it very well."

On a happier note, there are the tiniest green shoots of a possible romance for Ridley with his late wife Kate's friend, Annie, played by actress Julie Graham.

"Annie and Ridley run the jazz club Marlings together," says Adrian. "Annie's the only person Ridley opens up to and as the second series progresses, we see their relationship beginning to change. We're not talking wedding bells or anything like that, more a shared bag of chips at the end of the night! He's never considered her in a romantic light before - he just wasn't ready but when another guy shows up and starts taking a massive interest in Annie, Ridley thinks, 'Hang on a minute - why am I not happy about this?'.

He's known Julie for years and calls her a good mate who he loves working with on the show.

"It's great when you get to work with friends," he says. "It brings a real warmth to the acting."

And the cast surely needed that. Filmed over winter in a location north of Manchester, at times the weather was as bleak as some of the storylines.

"Oh, it was really cold. There was one scene that we did way up on the Moors," says Adrian. "It was snowing and I had to go inside every two takes because my face was frozen. It was so cold you'd end up with this kind of terrible smile on your face trying to speak.

"So I had to go and sit by the fire to kind of relax. But then again, the sun comes out and it's freezing but it looks amazing, and it's snowing up in the hills and you think, 'Wow, this is going to look great on screen'."

In the three years since we met Ridley, things have started to move on for him, although understandably he continues to be haunted by the loss of his wife and daughter.

"I wanted to show some progression - I think it's important to show that you can move on from grief - but on the other hand, the loss will always be there," says Adrian. "I once met someone who had lost his daughter in a car crash and he kept thinking that she would show up again somehow.

"It was a kind of a psychological thing where it was so hard to believe she was dead, he thought that someday he'd turn a corner and she would be there. This man couldn't help projecting his daughter onto other young women he met. I wanted to incorporate this into Ridley and that's what happens in the first episode of this second series."

Over the past year Adrian, who's married to actress and casting director Anna Nygh with whom he shares grown-up daughter Madeleine, has swapped the screen for a treading of the boards in a smash hit production of stage musical Kiss Me, Kate. Talk about mixing things up!

"That was so different," he laughs. "With Ridley, you're up very early in the morning and you're working outside, and you're out until 7pm, five days a week. Being on stage is more like a contact sport - it's physical, you're singing and dancing, you're running around, you're learning your lines, you're getting the lines out. It's eight shows a week, and each show is a workout.

"You have one day off which is Sunday. So it's a real grind or it can be." Luckily, he says, he was starring in a "good show".

He adds: "It was exciting but tough work. It's much tougher work than TV, physically speaking. On TV, there are other demands, for example, mentally - we have to do a lot of work on the scripts. But the variety is good."

What else is good - very good indeed - is that after months and years of speculation and rumours, it seems that Line of Duty is to return with Adrian, 67, reprising his role as Superintendent Ted Hastings with Vicky McClure as DI Kate Fleming and Martin Compston as DI Steve Arnott. Oh 'Jesus, Mary, Joseph and the wee donkey' - as Hastings himself might say.

"It will happen," Adrian insists. Jed Mercurio is writing new scripts and we're really excited about getting our hands on them - we're just waiting for the BBC to make an official announcement. Me and Vicky and Martin really want to do it and hopefully we'll be back filming in Belfast next year.

"Last time we were there it was during Covid and we couldn't go out so it will be great to be back and have a bit of fun. It will also be nice not to have Jed constantly screaming at us to put our masks back on."

It would be more than nice to see more of Ted off duty. Relaxing perhaps. Maybe even having a night out at a karaoke bar? Don't get your hopes up, though!

"Yeah, I'm sure you would like to see that," Adrian laughs. "But that's just not Ted's territory. He'd never do anything like that."

More's the pity. He'd make a top job of Little Donkey.

• Ridley airs on ITV and STV from tonight at 8pm, and is available to stream on the same day