Is John Audley there? Get done as soon as possible, for there are persons sufficient for another audience. John Audley was a noted showman and actor; when his platform was full, he taught the ticket collector to poke his head behind the green curtain, and cry out: “Is John Audley there?” This was a signal to the actors to draw their piece to a close, and clear the house as quickly as possible. Audley taught this trick to Richardson.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894