Midnight Retired
After the War our Government put an embargo of 60 years on matters relating to the Dutch SOE fiasco that was effectively delivering all Dutch agents into the hands of Herr Giskes of the German Abwehr,I recommend reading 'Between Silk and Cyanide ' by Leo Marks to get a good appreciation of that story .
I have a feeling the SOE files now in the National Archives at Kew, some of which I've read, mention Col Giskes and his very successful (for the Germans) "Englandspiel". NA file series HS 6 refers.
...also a bit more here:
Real History. However at the end of this page there is reference to some files still being witheld, but why I suppose we'll never know. They are now over 67-years old and it appears odd to be keeping back information after all this time.