By all accounts, the visit by the delegation of leading Chinese businessmen was a resounding success. Hidden away in sleepy Shropshire, Grainger and Worrall is a world-leader in the precision casting business. It prides itself on turning molten metal into complex components used in wind turbines, racing car engines, and speedboats. But not all its products are so benign. The firm also makes key parts for military drones, vehicles, and artillery; its website is illustrated with photos of RAF helicopters, Royal Navy destroyers and Army tanks. And it’s with these products in mind that the team from the China North…