Ronald Psmith is Rupert Psmith in most of the novels, until his name is changed to Ronald Eustace is Leave it to Psmith. He wears a monocle, is tall & thin, immaculately dressed, and very witty. A version of him is worked into other books as Rupert Smith, an American.
"Wodehouse said that he based Psmith on Rupert D'Oyly Carte (1876–1948), the son of the Gilbert and Sullivan impresario Richard D'Oyly Carte, as he put it "the only thing in my literary career which was handed to me on a silver plate with watercress around it". Carte was a school acquaintance of a cousin of Wodehouse at Winchester College, according to an introduction to Leave it to Psmith. Rupert's daughter, Bridget D'Oyly Carte, however, believed that the Wykehamist schoolboy described to Wodehouse was not her father but his elder brother Lucas. Lucas was also at Winchester."Psmith in Wikipedia