Dr Sowerbutts tells Sgt Grimshaw that Sherlock's mother is half-French, a member of the "very well thought-of" artistic French family Vernet, as mentioned in the 1893 short story "The Adventure of the Greek Interpreter" by Sir
Arthur Conan Doyle (in his novelisation author
Gerald Frow enlarges that Sherlock's grandmother - his mother's mother - was Horace Vernet's sister). Conan Doyle also referenced "country squires" in the detective's lineage during the same text.