I see. Written by a New Zealander? If not, that's rather surprising. I always get a kick out of seeing little old NZ mentioned in international literature. Except for when Sergei Lukyanenko called LOTR an "American movie" in whichever book it was. I digress.
Our policement aren't armed and the air force possesses about 3 helicopters and one ancient Hercules that may be falling apart, and our navy has perhaps one boat. If mutants swarmed the place, we'd be screwed. Hell, if anything swarmed the place, we're screwed.
John Wyndham is English, actually. It's a post-Apocalyptic type story (with a more successful Apocalypse than Fallout) and Labrador in Canada and New Zealand were selected as being both remote enough to have survived and basically on completely opposite sides of the world (for story purposes). New Zealand is apparently the most advanced society on Earth in the book, and the only one to have progressed from the time of the war.
It's a good book if you are into Sci-Fi.