Cay Van Ash (born in Sussex, England in 1918; died in Paris, France in April 1994) was a Professor of English Literature at Waseda University in Japan and a writer.
In 1971, Rohmer's widow Elizabeth contacted Van Ash to help her complete a biography of her husband, Master of Villainy, which was published the following year.
Whilst teaching in Japan, Van Ash was licensed by the Rohmer estate to write a continuation Fu Manchu novel, Ten Years Beyond Baker Street (1984).
Set in April 1914 in Sussex, it featured Dr. Petrie calling Sherlock Holmes out of retirement after Nayland Smith is abducted.
At the time of his death in 1994, Van Ash and his wife were living in Paris where he was researching the novel's setting.