The truth and the facts aren't necessarily the same thing. Telling the truth is the object of all art; facts are what the unimaginative have instead of ideas.
Beautifully shot, impeccably paced, it was a clear, unrelenting look at the National Trust, its friends and enemies, and it makes you want to burn your passport and beg the Luftwaffe to have another go.
Science fiction is never about the future, in the same way history is rarely about the past: they're both parable formats for examining or commenting on the present.