Or perhaps it was the other way around.
Shaffer also wrote "Equus," "Amadeus," "The Royal Hunt of the Sun" and "Five Finger Exercise," all plays eventually made into movies.
Universal, which was busy in those days scouting Broadway productions, immediately snapped up the film rights to "The Public Eye"/"The Private Ear" and then didn't know what to do with two one-act comedies. Both were eventually made into very pleasing, if little-seen movies.
"The Private Ear" was filmed by Brian G. Hutton in 1966 and retitled "The Pad and How to Use it" - a title inspired a little too obviously by Richard Lester's successful "The Knack and How to Get It."
Essentially a glorified TV movie that was released, albeit briefly, to theaters, "The Pad and How to Use It" deserves to be rescued.
"The Public Eye," finally filmed in 1972, had better luck. Well, sort of.
It was adapted for the screen by Shaffer himself and directed by the estimable Sir Carol Reed.
When Belinda becomes aware that she is being followed, she's flattered by the attention and starts to play games with her potential paramour. The private eye figures everything out - that the wife isn't unfaithful at all, but merely looking for something that her husband isn't providing - but that she's getting from him. It's a truly enchanting film.
"The Public Eye" made it into theaters - but just barely. Universal opened in unannounced and without any advance critics' screenings.