At the end of each performance, the cast request that the audience do not reveal 'whodunnit'............hence the play has been going for so many years.
I fully intend to see it at some point, and have made it my business to avoid finding out 'whodunnit'.
I thought it was ok - alot more comedic than I thought it would be. They played it a bit like a farce, but I suppose the style changes as the actors and director changes.