Emil Ludwig wrote many books on historical subjects, especially European history, and some fiction. He and his wife Elga became friends of King. Ludwig drafted a short book about King, and showed the text to the Prime Minister and to Joan Patteson for comments. This illustrated book was published under the title Mackenzie King, A Portrait Sketch (1944).
Ludwig visited King several times. The diary for February 13, 1944, contains a long account of a conversation with Ludwig. On another occasion, King commented about Ludwig: "His visit was a real inspiration and pleasure to me." (Diary, June 11, 1944)
In the King Papers, there is a file of correspondence with the Ludwigs, and letters between King and Elga Ludwig after her husband's death.