worryingly jolly batman

It would be dangerous to assume that any given police offier is not armed while on duty. Especially plainclothes officers. Patrol cars do carry guns and officers are authorised to use the firearms if confronted with an appropriate situation (say, a nutter with a shotgun). Once upon a time, having to get permission to carry a gun was a big deal but it happens a lot more now. Armed police are a reality in New Zealand - not every copper on the street, it's true, and they prefer not to show weapons if they can manage it, but they're there.