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.
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.
Once upon a time, a historian told me that the most important choice a new historian could make was of his or her specialist subject. Most of the good stuff was far too overcrowded, so you had to pick about in the exotic and extinct. His recommendations were the Picts or the Minoans, because hardly anything was known about them and you could spend a happy lifetime of speculation.