The British National Archives at Kew come up with surprising finds of one sort or another in every monthly bulletin. The latest offers postcards and photographs from World War I, including this charming wish for "A Pleasant Christmas."
There's also an interesting collection of papers about the astrologer hired by the British government to conduct stargazing psyops against Hitler, who was a great believer in such things:
Louis de Wohl (KV 2/2821)
De Wohl was a Hungarian astrologer and author who came to the United Kingdom in 1935 and spent much of the war in official employment on propaganda work for the Special Operations Executive (SOE), the Political Warfare Executive (PWE) and other agencies. The work was based on the assumption that Hitler was heavily influenced by his own astrologer, so that by employing their own prominent astrologer, the British could sway his thinking.