Sun Times 30ac (Clue: A first-class return to island capital, -P-A). Answer appears to be APIA. I understand the 'a' and the 'a1' but where the hell does the 'p' come from?
Many thanks folks. Not sure if I'm convinced by any of them, but they're all better than anything I'd come up with! I'd probably go for 'PA' as in 'per annum'.