think Paul W. himself explained that it's about the band themselves - they formed the band as schoolmates (they used to "jam" together, hence the name), and at the time thought they'd be mates forever, but as they grew up they grew apart (and indeed eventually split up). Thick as thieves is just a phrase for close friends, but the lyrics play on the words, and conjure up a picture of schoolboys nicking stuff....
think Paul W. himself explained that it's about the band themselves - they formed the band as schoolmates (they used to "jam" together, hence the name), and at the time thought they'd be mates forever, but as they grew up they grew apart (and indeed eventually split up). Thick as thieves is just a phrase for close friends, but the lyrics play on the words, and conjure up a picture of schoolboys nicking stuff....