The Secrets of Potsdam by William le Queux

I suppose that none of your British friends have ever heard the name of Thyra Adelheid von Kienitz.

She was a funny little deformed person, aged, perhaps, seventy, widow of the great General von Kienitz, who had served in the Franco-German campaign, and who, before his death, had been acknowledged to be as great a strategist as your own Lord Roberts, whom every good German -- I did not write Prussian -- salutes in reverence.