When the regular actors in this series turned up for the first read-through of this episode, they were astonished when guest star Emlyn Williams handed each of them a new version of the script written by himself, keeping to the broad outlines of the story, but rewriting the dialogue and giving himself rather more lines. No-one had asked him to do this, and he was carefully informed in no uncertain terms that John Mortimer's original script would be used with no alteration. He complied.