The end and aim of spying in all its five varieties is knowledge of the enemy; and this knowledge can only be derived, in the first instance, from the converted spy. Hence it is essential that the converted spy be treated with the utmost liberality.
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.