For decades, New Zealand's biker gangs fought each other for turf, cash and kudos. Violence between its two biggest outfits, the Mongrel Mob and Black Power, often turned deadly, and acts of cruelty shocked the public.

Then, in the mid-90s, a new, potent drug worth billions arrived on the country's pristine shores - and with it a wave of foreign narcos looking to take control of what might be the world's most profitable black market.

The gangs gave thousands of disaffected Maori and Pacific Islanders an identity. Meth—known locally as P—changed everything.