According to Nancy Mitford in The Letters of Nancy Mitford and Evelyn Waugh (p. 251), Leautaud was an eccentric literary critic and diarist who said he loved cats and dogs more than people, lived on nothing but potatoes and cheese for eight years, and never travelled further than Calais.
Mavis Gallant described him in her Paris Notebooks (Toronto: Stoddart, 1988):
He was mean, slanderous, and cruel; he could also display generosity and great delicacy in his judgments.
He wanted to say before he died, “I regret everything,” words, he said, “that will sum up my life.” The last thing he did say before dying in his sleep was, “Foutez-moi la paix,” [“Leave me the hell alone.”] which was more typical. (p. 151)
I must learn more about him!