With a creak of wooden cogwheels, the two men turn the huge sails into the North Sea breeze coursing not across waves, but the flat Dutch polders outside Amsterdam. “We bring the mighty blades to the wind so that the work can begin,” says windmiller Jippe Kreuning, 30, flanked by Sjors van Leeuwen, a volunteer who is more than twice his age and sports a jaunty pilot’s cap. Soon the sails of the De Bonte Hen (the colourful hen) oil mill spin freely as deflection shafts transfer the wind’s force to the twin millstones weighing several tonnes. Beneath them, linseed is ground to produce oil for a …