It became clear very early in the war that the RAF was 'wasting' a great many planes, in the sense that planes crashed and could no longer fly. Nuffield set up a network of Civil Repair Organisations which would collect the crashed aircraft, bring them to repair factories in various parts of the country and, largely by trial and error, put them back into airworthy condition. This was a massive operation that provided vital support in the Battle of Britain.
Nuffield also built tanks, first the Cruiser and then the Crusader and the Cromwell. These tanks were initially outgunned by Germany's Panzers, but later with a 6lb gun gave as good as they got. In the Desert War, at least initially, they proved unreliable, but Nuffield flew out a team of engineers to investigate and address the problems. In addition to tanks, Nuffield championed the self propelled gun, in particular, the Bofors. They manufactured ammunition and much else.
It was said that the motor companies were ideally placed to manufacture anything out of metal, and this they did.