For some unknown reason, my iCloud account got itself locked about 45 minutes ago, I had to reset the password & thanks to Apple's paranoia, some 3rd party apps like Outlook on the Lumia 1520 & BusyCal on the Mac needed new app-specific passwords.
This process wasn't helped by iClod (sic) Keychain failing to update the new password until about the 7th login attempt.
All OK, now, though.