Sleep runs on temperature. Your body lowers its own to fall asleep, and the range it needs to stay in is narrow. A sheep solved that problem long before anyone thought to make bedding out of it.

Wool absorbs up to a third of its own weight in moisture without ever feeling damp, then gives it back to the air. Taking moisture on warms it a little. Giving it back cools it a little. So the temperature under the duvet gets nudged back instead of swinging. That is what temperature regulation means. Down manages under a tenth of its weight. Polyester, under one percent, does none of it.

Ours is New Zealand strong wool from Tairāwhiti Gisborne, needle-punched into one continuous fleece rather than blown in loose. It drapes evenly across the bed and stays where it is put. Pure wool and nothing but. No antibacterial finish, no biocide, no flame retardant, because wool has never needed them.

Two weights and six sizes, in a 300TC cotton lining, made by hand in our Auckland workroom.

Known in Australia as a wool quilt or doona, and in New Zealand as a duvet inner.