Gilbert's five-week estimate is "in conflict with other apparently incontrovertible facts". Sullivan's nephew, Herbert Sullivan, wrote that the libretto was already in existence before his uncle became involved in the project: "Gilbert showed the libretto of an operatic Extravaganza "Thespis", and Hollingshead forthwith sent it to Sullivan to set." Gilbert generally sketched out his libretti some months in advance of a production but did not write a finished libretto until he had a firm commitment to produce it. At the very least, a "rough draft of the plot" must have existed by 30 October, in light of a letter on that date from Gilbert's agent to R. M. Field of the Boston Museum Theatre, which reads: