HOW do you know your star is in the ascendant? Scott Reid had an inkling when he saw his face tattooed on a stranger’s leg. Then there were the people sharing pictures of themselves dressed up as him at Hallowe’en. Oh, and a Glasgow bar named a cocktail in his honour (a shot of Midori and creme de menthe if you fancy it).

Reid, 23, burst on to our television screens in BBC Scotland comedy series Still Game last autumn. The Glasgow-born actor went on to win a legion of fans for his role as Methadone Mick, a recovering drug addict with a heart of gold.

In one memorable scene, the show’s leading men, Jack Jarvis (Greg Hemphill) and Victor McDade (Ford Kiernan), help Mick spruce up ahead of a job interview.

As part of his Craiglang-style extreme makeover, the pair take him to a backstreet dentist where the hapless Mick ends up with a comical set of gnashers that bear an uncanny resemblance to the toothy grin of former footballer Frank McAvennie (sorry, Frank).

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The character became an instant hit. Within minutes of the episode airing Reid was hit by a tsunami of emails, text messages and social media alerts. He sensibly turned off his mobile phone and went to bed.

When Reid switched it back on the next morning, his jaw dropped. “I had 3,000 new Twitter followers overnight with each notification coming individually,” he says. “It was the most bizarre experience.”

Further testament to that soaring popularity came when fans snapped up 10,000 sets of replica rubber teeth during the Still Game Live 2 shows at the SSE Hydro in Glasgow this year. Which takes a bit of getting your head around, admits Reid.

“It is mad. There is no other word for it.”

He is quick to credit Still Game creators Kiernan and Hemphill for the leg-up. “The success of Methadone Mick is down to what Ford and Greg wrote,” he says.

“They created this incredible character and took a risk bringing a young, fresh-faced character into Still Game.”

Reid arrived on the duo’s radar thanks to a role in the Paul Higgins and Ricky Ross penned musical, The Choir, in 2015. Reid’s friend and fellow actor Julie Wilson Nimmo, who is married to Hemphill, had taken her husband along to the show at the Citizens Theatre in Glasgow.

A few months later, Hemphill got in touch. “I received a Twitter message saying: ‘Hiya, brother, I have this part in Still Game. Could you send me your mobile number? I would love to have a chat with you about it.’”

Reid’s first thought was that someone was pulling a prank. “It was a rainy day and I was sitting on top of my bed at the house I was living in at Seven Sisters, north London,” he says. “I hadn’t been getting any luck with auditions around that time.”

As Hemphill outlined the role of Methadone Mick, so began a remarkable journey. “I was straight off the phone and on to my dad saying: ‘You’ll never guess what. Greg Hemphill just called me,’” says Reid, who had to swear his family to secrecy about the part.

Hemphill announced last month that a new series of Still Game is in the pipeline. Will Methadone Mick be back? For now, Reid is keeping his cards close to his chest.

“The great thing about Mick is that he can disappear or come back, that is the type of character he is,” he says, carefully. “He is the kind of guy who could have got a job and disappeared down south for a few months. My door is open. I would love to return to Still Game, so fingers crossed.”

After wrapping filming last summer there was barely time to draw breath. Less than a week later Reid was on his way to Belfast to shoot BBC police drama Line of Duty.

He played Michael Farmer, a known sex offender with severe learning difficulties, who is arrested on suspicion of kidnap and murder. With the storyline centred on a potential miscarriage of justice, it was a starkly different role to the cheeky chappy persona of Methadone Mick.

“Polar opposites,” he confirms. “The vibe on set was completely different. That was a real learning curve. I had come from Still Game where there was just as many laughs on set when you are doing a take as there was when you’re in the makeup truck or on unit base.

“Line of Duty was fun, but in a very different way. It was fun getting into those really meaty dramatic scenes.”

The actor is currently playing the lead role in the National Theatre’s award-winning touring production of The Curious Incident of the Dog in the Night-Time. Adapted from Mark Haddon’s bestselling book, it tells the story of 15-year-old Christopher Boone, who falls under suspicion when his neighbour’s poodle Wellington is found speared with a garden fork.

“The tour has been incredible and quite life-changing,” he says. “It has pushed me to the limit as a performer: emotionally, psychologically and physically.”

He is unlikely to be idle on the work front any time soon. The Curious Incident of the Dog in the Night-Time tour runs until September. As that draws to a close, Reid will put out feelers on prospective roles.

Ultimately, says Reid, the goal is fulfilment. “By God, there are a lot of actors who are miserable,” he says. “You hear stories of guys at their peak who turn to drugs or drink, you hear those stories all the time.

“Trying to be happy and keep family around, that is probably the biggest aim. There is a moment every day where I go: ‘This is the best job in the world.’ I’m passionate about it and I’ve set myself the aim that nobody will work harder than me.”

The Curious Incident of the Dog in the Night-Time is at the King’s Theatre, Glasgow, from August 14 to 19. Visit curiousonstage.com