Premise: Cowardy Custard is a musical revue and was one of the last Noël Coward shows staged during his life. It was devised by Gerard Frow, Alan Strachan and Wendy Toye. A book, also titled "Cowardy Custard", was published in connection with the revue, similarly celebrating the Coward image.
Hypothesis: The book "Cowardy Custard" has no relation to the musical revue.