That is true I agree but I know not to go on a Monday as that's his day off and given that he does his radio show from 11AM to 1PM on Sunday's then I can see how he wouldn't want to work on a Sunday, however I'm sure his walk on study or whatever that name is, it's not an understudy but I forget the right name now something like that would probably do it providing Ian isn't off who plays Wilbur because he does both Edna and Wilbur.
But yes it would make a killing I'm sure if theatre's in the WE opened on Sundays, even if it was the Matinee like you said

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