Question: What is the date of death of Susan Buchan, Baroness Tweedsmuir's husband?
Sentence (from "Susan Buchan, Baroness Tweedsmuir"): Susan Charlotte Buchan, Baroness Tweedsmuir ("née" Grosvenor; 20 April 1882 – 21 March 1977) was a British writer and the wife of author John Buchan.
Relevant evidence: Yes