I clicked on that link and there is mentioned DB's svengali tour. obviously svengali refers to the well known novel about the hypnotist svengali and his subject, trilby.
not so well known is where the author gained his inspiration for the novel.
from a book entitled, Secret, don't tell, The enclyclopedia of hypnotism by Carla Emery. page 1-
the novel trilby, published in 1894 introduced the basic sordid facts of hypnotic exploitation to a mass readership. by the vehicle of fiction, it presented important facts about abusive hypnosis. Dumaurier's tale of poor trilby stimulated a much needed public awareness and discussion of unethical hypnosis.
an Englishman, with a french name, George Du maurier, wrote his last and most famous novel, Trilby, about hypnocontrol.
Du maurier got the idea for his tale of Svengali's cruel domination of his hapless hypnotic subject from viewing a demonstration of a subject's complete amnesic, dissociation in a hypnotist's office. the young female whose hypnotic submission was demonstrated to Du maurier was an unknowing, chronic, hypnotic subject, an artificially-split personality. the novelist watched her be hypnotized, made to obey commands under trance, then awakened. he saw her obedience to post-hypnotic commands and her rationalization of them as freewilled choices. he observed her total unawareness of her previous trance state.