Usually a windmill has three blades facing into the wind. But Whisson's design has many blades, each as aerodynamic as an aircraft wing, and each employing "lift" to get the device spinning. I've watched them whirr into action in Whisson's wind tunnel at the most minimal settings. They start spinning long, long before a conventional windmill would begin to respond. I saw them come alive when a colleague opened an internal door.

And I forgot something. They don't face into the wind like a conventional windmill; they're arranged vertically, within an elegant column, and take the wind from any direction.

The secret of Max's design is how his windmills, whirring away in the merest hint of a wind, cool the air as it passes by. Like many a great idea, it couldn't be simpler — or more obvious. But nobody thought of it before.

With three or four of Max's magical machines on hills at our farm we could fill the tanks and troughs, and weather the drought. One small Whisson windmill on the roof of a suburban house could keep your taps flowing. Biggies on office buildings, whoppers on skyscrapers, could give independence from the city's water supply. And plonk a few hundred in marginal outback land — specifically to water tree-lots — and you could start to improve local rainfall.