It's been less than 10 years since Nicky Spence started again.

At the age of 21 the Scottish tenor was, in his own words, under-trained, overweight and fast on the way to becoming a commercial sell-out.

"I had seriously lost my way," he says of the year he spent recording pops classics and Scots songs for Universal and touring with the likes of Katherine Jenkins and Shirley Bassey. "I had a cliché of a manager who told me he was 'gonna make me a star'. But none of it was real. I could see my own shelf life." Eight years later, Spence is one of the most respected operatic tenors of his generation – the young talent of choice at opera houses in London, New York and indeed Glasgow. What's more, he's happy.

The morning of our interview he bounds into the café with blithe, puppyish flamboyance. "You smell fabulous," he tells me between air kisses and orders coffee with a mawkish fizz that visibly riles our gruff breakfast waiter. With his baby-blue eyes, rosy lips, extreme fair hair and hyped gestures Spence makes an oddly boyish diva. But he is far too funny and pragmatic to be a real opera luvvie. He's from Dumfriesshire and supports Queen of the South. He loves a good ceilidh and a night in watching The Great British Bake Off.

Anyway, he's got every reason to be bubbly. In the three years since finishing studies at the National Opera Studio his career has skyrocketed, and rightly so. He became a Young Artist at English National Opera, where he premiered a lead in Nico Muhly's new opera and earned critical praise as the Novice in Britten's Billy Budd. Last year he made a suave Baron Lummer in Scottish Opera's Intermezzo, and two weeks ago gave a beautiful cameo as the Young Sailor alongside Nina Stemme and Ian Storey in the BBC SSO's Tristan und Isolde. Next week he debuts as Tamino in Scottish Opera's new production of The Magic Flute.

There's a nice symmetry here: it was a Scottish Opera production of The Flute (Martin Duncan's in the early 1990s) that was the first opera Spence ever saw. Growing up in Dumfriesshire, he spent his childhood "steeped in the Scottish traditions of recitation and country dancing", he says. "I went to a village comprehensive in Thornhill where you could do quite a lot of poofy stuff without getting beaten up." Spence describes it as a creative area with Andy Goldsworthy eggs on the hill by the school and a culture of "doing our own thing. We'd always be forming bands singing Spice Girls one year, Ave Maria the next. Everyone worked at the local chippy. I did my time there, down the stairs peeling the tatties for £1.70 per hour."

Acting was his initial passion and he toured with Scottish Youth Theatre and National Youth Music Theatre as a teenager. Then at 15 his music teacher suggested he try singing lessons, and soon "singing was the only thing I wanted to do". A local accompanist offered him a spare ticket to The Magic Flute in Glasgow, and after the show Spence wrote to Derek Clark, SO's head of music, explaining he wanted to be an opera singer.

"It was an uppity letter – typical overconfident teenager stuff. I'd forgotten about it until Derek showed me it during Intermezzo last year." Clark listened and encouraged him to train. Auditioning for the Guildhall, Spence found himself surrounded by choral scholars. "I knew my voice was all over the place, but also that I was the only one who could tell a story through words."

His natural talent turned heads at the Guildhall, and in the commercial world. He jumped at a high-figure record deal but quickly realised "it was never going to go anywhere vocally. It was an awful experience."

Tellingly, Spence's full discography is not available on his website: there's a part of his past he'd rather keep behind him.

At college his teachers were "quite encouraging" about the record contract, "but I knew I was under-trained. I found myself in the gold medal final at the Guildhall and simply wasn't equipped. It was public humiliation and took a lot of my confidence away. I had a crazy schedule – I reckon my hair receded by about 3 inches in that one year. So when it got to the point of doing another album I decided it wasn't for me."

Spence ditched the contract and went back to college full-time, which he describes as the best decision he ever made. "My voice was still changing," he says. "I needed more tools if I was going to do this properly. So I worked like crazy with a new teacher who I've been with ever since." What did he look for in that new teacher? "Someone who wouldn't bull***t me."

He still makes an effort to sing "as much serious stuff as possible because it's quite easy for people to cast me in comic roles. I'm a big barrel of fun on stage but, especially in the beginning, I wanted to say I was about more than that." Recent "serious" roles have included Stravinsky's Tom Rakewell and Nico Muhly's Brian in Two Boys.

As for Tamino? Spence describes working in Scotland as "coming home" and working with director Thomas Allen as "a great honour. He's been a sort of mentor to me in the past, and at first I was intimidated because he's sung this opera so many times himself." Allen made his Metropolitan Opera debut as Papageno in 1981. "But as a director he usually steers clear of talking to me about singing. He's so young at heart: mischievous, a twinkle in his eye, running the room with his charisma and his knowledge."

Allen's productions of The Marriage of Figaro and The Barber of Seville for Scottish Opera have already proved him a singers' director who understands the beauty of not over-choreographing his cast. "I'm enjoying playing a heroic young prince," says Spence. "The straight man to Papageno's funny man. And I'm really enjoying the strength of not doing too much on stage."

Does he ever contemplate "what if" scenarios, the alternative universe in which he stuck with that record contract? "I could be presenting Daybreak by now! And I wouldn't be happy. I wouldn't be in control. Now the work I put in comes out the other end. It feels real."

The Magic Flute opens at the Theatre Royal on October 17.

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