The Mystery of the Red Barns in Norfolk

I came across a few interesting news articles from 2015 that, while a bit far afield from the story of Josef Jakobs, are intriguing nonetheless (see links below). The stories centre on some Dutch farmers in Norfolk who were apparently building secret airfields and hangers for Germany's invasion of England. Barn built by Dutch farmers in Norfolk (from Daily Express article ) For 4 years, commencing in 1936, Dutch farmers of the East Anglian Real Property Company had been building huge barns and apparently preparing fields to serve as air strips for the German invasion. The RAF, on the hunt for new air strips in 1940 saw that all the likely looking sites were already occupied by suspicious barns with red roofs, chicken coops in the shape of swastikas and fields devoid of crops. The Dutch farmers were all rounded up, arrested and interrogated. While some newspaper articles call them "spies", this seems highly unlikely as all were later released. Although... some news