In 12 months, a single catchy tune has conferred international stardom on Chicago band Plain White T's. Yet both the drippy boy-meets-girl-tune, Hey There Delilah, and the band themselves, have been on the go for years, they tell Tony Clayton-Lea.

PERSEVERANCE really does pay off; either that, or obsessive compulsion kicks in and refuses to relax. So implies Dave Tirio, formerly drummer and now guitarist of Chicago's Plain White T's.

Just in case you haven't been listening to the radio, or watching certain types of television programmes over the past six months, Plain White T's are the US band du jour; they have, in the space of less than a year, crossed over from being totally unknown outside the US to being feted in more countries than we care to list.

The reason for the change of fortune is a song called Hey There Delilah, a drippy boy-meets-girl tune wherein girl doesn't want to know and boy writes a song about her, explaining that when the song is a Grammy winner and he's rich and famous, she'll be sorry she didn't leave her sad sap of a boyfriend for the nascent rock star success story.

It's a cute song, beloved in the main by teenage girls who dig its sense of destiny and who feel for its bruised protagonist. It is, however, not so much a sleeper hit as a song that has been in a coma for several years. In other words, don't talk about overnight success stories to Plain White T's.

"We've been around for a decade," sighs Tirio, who by this stage must be bored to tears having to explain that his band have been around in one shape or form for so long. "Being catapulted into a very high-profile area in such a short space of time - despite the fact that we've been around for quite some time - is a bit shocking, to say the least.

For 10 years we've been doing the same thing, travelling around the US in a van, trying to tour as much as we can and trying to create as big a fan base as possible; it's taken a long time to do that. It takes quite a while to get around America and play six to seven times in each city to get to the point where people are familiar with your music. It's a lot of work to get that fan base going.

"But now in a matter of months we feel that we're bigger overseas than we are in the States. It's a bit crazy for us, and it's one of the most amazing things to have happened to the band. We were always used to things being a struggle, fighting for this and that, grinding it out, but now to have success come so easily and without all the blood, sweat and tears is truly incredible."

It is, says Tirio, a lesson in persistence, a facet of the band's collective character. When they started out in 1997, recalls Tirio, it was them and several handfuls of other like-minded rock bands with the usual mutual goal of worldwide success and fan adulation.

When things got too difficult for some, Tirio says, they quit because they reckoned they were too old for the game; they got real jobs and settled down. The key to Plain White T's was, he reckons, "weird blind faith. We kept going and always thought something good would happen.

And it did - every year something good happened. It might have been small at the time but it was a big deal for us - like, say, playing support to one of our favourite bands and playing bigger venues with them. Or the first time we got onto college radio, or the first time MTV played one of our videos.

"You can't blame them too much, though, because we had those struggles with our conscience, too. We had every struggle in the book; we've had guys quit the band because they felt they were running to stand still, never moving forward. I know that feeling very well."

Hey There Delilah has changed everything."In true fashion with us, that song took ages to catch on with people. It was another struggle. It's been churning around in the underground for about five years ... Then it became an online, MySpace thing. It was simply a grassroots online favourite. It's funny to think how long it took to become an overground hit."

Has it become something of an albatross? "I always thought it might be," admits Tirio. "Rather than pigeonholing us, though, it's actually opening up new areas for us. Because of its success we now have the freedom to make whatever kind of songs we want."

Was 2007 a great year, then? "We're all very happy with what happened to us last year. For the first time in our lives none of us are broke, and that's an amazing feeling. We're enjoying the hell out of it."

Plain White T's play Dublin's Ambassador Theatre tomorrow night. Their latest album, Every Second Counts, is out through EMI.