When singer Marie Fredriksson was diagnosed with a brain tumour in 2002, all thoughts of the group touring and recording again seemed gone. Yet, several years later, they are returning to the SECC in Glasgow tonight as part of a comprehensive world tour.

It's unsurprising, then, that guitarist and songwriter Per Gessle has an upbeat tone in his voice as he recounts how the duo found themselves together again.

"When Marie got ill in 2002, everyone thought the band was over," he says. "I did a lot of things on my own, and I did a club tour of Europe with my own band in 2009. When I played in Amsterdam, Marie and her husband were visiting, and I convinced her she should join me onstage for a couple of Roxette songs.

"To my surprise, she did and it was one of those magical moments – people were crying everywhere and it was amazing. She got so much power from that moment and a couple of weeks later she called me up and asked if I wanted to write a new Roxette album, which I did."

That album became 2010's Charm School, and in between the duo played several shows as part of the Night Of The Proms in Germany and Holland, limiting themselves to a few songs each night. Yet the singer's strength continued to grow, and a series of dates soon expanded more, and more, and more -

"We're doing almost two hours each concert and to see Marie as she is now, it's unbelievable," says Gessle.

"She lost a bit of her right eye so can't see to the right, and is cautious when she moves, but her voice is intact. The reception we've been getting is amazing – it's been by far the most entertaining tour I've ever been on and has been very emotional for all of us."

Gessle promises a party atmosphere when they play in Glasgow, with a set that will be heavy on the hits. Those songs, such as The Look, Dressed For Success and It Must Have Been Love, all represent an interesting cross between two pop worlds – those of Europe and the United States.

Roxette were the Swedes with enough savvy to conquer the American charts while going at their own pace, avoiding a move to Los Angeles in favour of staying in Stockholm. For Gessle, that decision was vital in ensuring their sound wasn't tampered with.

"If we'd moved to LA we'd have sounded like any American band, so staying in Sweden really helped us out with the songwriting," he reflects.

"We were a top three most-played act in America three years in a row, and when you get that you get offers to work with songwriters and producers. I wrote You Don't Understand Me with Desmond Child [in 1995] but otherwise it was all our material and that made us stand out.

"Now when we do these songs we have a catalogue that is unique and that's why we're still selling tickets. We've played to nearly one and a half million people on this tour already and there's so many people who still have a connection to Roxette. I had thought that was over many years ago."

Key to sticking to their guns was the fact both Gessle and Fredriksson had already experienced pop stardom in their homeland, and were therefore experienced enough to anticipate any pitfalls with fame.

"It helped that Marie was 30 and I was 29 when we broke through, so we'd been around professionally for almost a decade in Sweden before we made it internationally," he says.

"That meant all our major mistakes with publishing rights and things like that had been made before we made it big in America, so we weren't swallowed up over there. If you look at Richard Marx and Paula Abdul, who were in the charts at the same time, they basically got forgotten, but Roxette are still going."

Despite a reliance on the old hits in a live setting, Gessle is still writing new material regularly. Yet he isn't too fussed over the fact the band's live sets only play a smattering of fresh songs.

"I saw Tom Petty the other week in Stockholm and he only played old stuff, but he was playing songs from 1981 that I'd never expected him to play," explains Gessle.

"It's the same with us because, from a fan's point of view, you want to hear the old stuff. But from a band's point of view it's always great to play new songs and try different ideas. We try to do both. The show isn't promoting anything new – we just want to play the big songs again. And if people are happy, then we're happy."

Roxette play Glasgow's SECC tonight. Visit www.roxette.se.