Jimson's father, based on a real person known to Cary, was an Academy artist who is heart-broken when Impressionism drives his style from popular taste.
Later in the book, he tracks down Sara Monday, his ex-wife, and tries to obtain an early painting from her that is worth a great deal.
As he is being taken to hospital, a nun who is nursing him remarks that he should be praying instead of laughing, "Same thing, Mother", replies Jimson, his last words.
In 1958, a film adaptation, also titled The Horse's Mouth, was released, with an Academy Award-nominated screenplay by actor Alec Guinness.
The film was directed by Ronald Neame, and starred Guinness, Kay Walsh, Renée Houston, Mike Morgan, and Robert Coote.