CHARLIE Reid can't explain why The Proclaimers song I'm Gonna Be (500 Miles) continues to resonate more than 30 years after its release.
Or how he and his identical twin brother, Craig, happened to write an iconic song that has survived various music trends to remain instantly recognisable within the opening bars to multiple generations.
What the proud Scotsman does know, is he remains eternally grateful.
"We love it completely because it keeps us going around the world," Reid tells Weekender in his thick Scottish brogue on a typically frosty Edinburgh morning.
"We can play Singapore, we can play Australia, the United States, Canada because of that song.
"The song is far bigger than the band really. There are bands that are far bigger than us and have sold millions of records who have never had a song that sustains like that one."
Nowhere in the world is I'm Gonna Be (500 Miles) more popular than Australia. The track was a No.1 hit in 1988 and it's subsequent album Sunshine On Leith reached No.2 on ARIA Charts. The enduring popularity of the Celtic folk-rock song has enabled The Proclaimers to tour Australia five times.
"We had a good record company in Australia at the time that really worked the record, the same as New Zealand and other territories," Reid says.
"Australia was spectacular when we had the hit records. I don't know, maybe the directness and the singalong quality of it. Things that appeal to people here [in Scotland] as well."
Certainly The Proclaimers have never matched the commercial success of Sunshine On Leith since, but despite some critics labelling them "one-hit wonders" they have continued to produce passionate, and increasingly political, albums.
Last year's Angry Cyclist, The Proclaimers' 11th studio album, received strong reviews back in their homeland.
The album focused on the issues of Scottish independence and Brexit, which has been tearing the United Kingdom apart politically since its 2016 referendum.
Reid and his brother are staunchly against leaving the European Union.
"The angry cyclist [metaphor] really represented the culture we've got, certainly in the UK, and in other parts of the world where politics have become very polarised and this feeling that people feel under threat," Reid says.
"Like an angry cyclist riding in London or somewhere getting hemmed in by buses and cars and feeling insecure."
The 57-year-old father of three became a grandfather last year and he says it's made him more concerned about the economic future of Scotland outside the EU.
"Hopefully it makes you a better person having kids and grand kids because you have to think about what happens after you've gone," he says.
The Proclaimers make their Newcastle debut at the Civic Theatre on May 21.