I KNOW THREE stories about the Moriori, a long-ago people who survived, in tatters, a determined attempt to eradicate them. The first goes like this: at a time that nobody can remember a group of men, women and children set off from the east coast of New Zealand and plunged into the vast ocean wilderness of the south-east Pacific. Nobody knows why they left the safety of the mainland – whether it was restlessness, or curiosity about what lay beyond the horizon, or grim necessity. They packed food and fresh water into a two-hulled canoe and, presumably, hoped for the best.

A few days into their voyage a mist closed around them until they could see nothing, wherever they looked. All they could hear were the thrashing of waves against the sides of their canoe and the cries of seabirds warning them of land. Cautiously they rowed on, until they came upon black rocks looming out of the fog, then an island and, within the perimeter of this chunk of earth, a safe harbour where they were able to land.