A Spy's story: R.H. Bruce Lockhart, British Agent (1918)

While this is not a diary, it is by all means a very good account worth reading, full of unique trivia and many fascinating historic details.

SOURCE FOR THIS PICTURE: Loretto School

Hugh Walpole's introduction notes that "...the great and final quality of this record is its honesty. Here, in this book, there are many of the most hotly-debated events in history. I suppose that there is no European alive today who, in an official position, was able at first hand to watch so long a sequence of the Russian crises as Lockhart. And it is fortunate for us that he is, by nature, so honest a man. You can test it, if you like, by his extreme honesty about himself. He conceals nothing; he is not concerned to conceal anything. He is really burning with a passion for the truth, and he sinks all personal prejudice in his love for it.".

The Great War Primary Document Archive hosts the book, British Agent, by R. H. Bruce Lockhart (G. P. Putnam's Sons 1933, New York and London). Hope you find it interesting!