Its not easy to write a script based around a confusing concept but there are better ways to handle it than tacking on a prolog. While the Doctors monologue about Beethoven is entertaining and educational it doesnt fit in with the rest of the story. Its also not necessary. There are ways to seed this information into the script so that the audience catches on. The opening sequence felt heavy handed and condescending as if the writer had no faith in the audiences ability to understand what was happening. Awkward handling aside, the idea of the bootstrap paradox is a fascinating thing to explore. Its appeared in Doctor Who before, most notably in the series three episode Blink and the series eight episode Listen. The concept of a causal loop, where future knowledge creates a past which in turn defines the future is perfect story fodder for a show that is based on the theory of non-linear time.