Steve, a lot of workers in German factories were forced labour, of all nationalties, political views and religions. There are a lot of credible stories of handfuls of sand or swarf stuck in with grease, Plaster or paper soacked in acid painted onto U Boat hulls. It was a dangerous occupation, if caught the results were fatal, often by nasty methods. But hey , what was there to loose? At least it gave what passed for life a purpose. Jersey airport, at the time considered one of the best equipped in the world, was only considered suitable for Light Aircraft by the German's. A local contractor was employed to mow the grass on the runways. The figure quoted is that the gras had to be 4 inches high. The mowere was set by a German officer at the start of the job. The operator then lowered the cutter, at te end he raised the cutter, this was checked by the officer at the end of the job.
It was only post war that this came to light.