For those with their motor insurance with Tower, either direct or via Trade Me Insurance (and perhaps through KiwiBank too), be aware that Tower will not insure you if driving off road. The exclusion from the current Tower wording is below, and I know the same is in my cover via Trade Me Insurance (underwritten by Tower). This is not a common exclusion in the insurance world.
Just something to be aware of (as well as their poor spelling).
"Your policy does not cover any loss, damage or liability arising from:
13. Using the car off-road using the car off-road, such as driving over open land, on beaches, riverbeds and sand dunes. This exclusion does not apply while you are launching or retrieving your boat from it’s own boat trailer."