Who is Rupert Morrison in the story "The Man Upstairs"?

Mr. Rupert Morrison is Beverley’s friend. The latter lends him his rooms at the Albany so that “he can be perfectly quiet and undisturbed” while writing his novel. He is the one who unknowingly spills the beans, to Annette, on who Beverley really is. He calls Annette’s apartment one day when Beverley is not around. The call is picked up by Annette, who accepts to take a message for Beverley. Rupert then complains to Annette about the parcels of music that Beverley has been sending to his rooms and which he does not know what to do with. He wants to know whether Beverley wants the music sent to his present residence. Upon further conversation with Rupert, Annette realizes that it is Beverley who has been buying her songs and who has, in effect, propelled her music career to its present greatness. She also realizes that Beverley has been buying Sellers’ paintings, too, and that his purchases have made Sellers a star artist. When she confronts Beverley with this information, he does not deny it. He tells her that he is a millionaire and that his real name is Bill Bates. She is infuriated by this confession and feels that Beverley is playing a dangerous game: “And you use your money, creating fool's paradises for your friends, which last, I suppose, until you grow tired of the amusement and destroy them. Doesn’t it ever strike you, Mr. Bates, that it's a little cruel?” However, it turns out that Annette, too, has secretly bought one of Beverley’s paintings, with an aim of promoting his career, so she really cannot hold his actions against him. Beverley loves Annette and wants her to marry him.