Complex sentence: Martin returned for two episode's on 19 and 21 April 2011, with his return bringing in 10.31 million people to watch on 19 April and 8.43 million on 21 April.
Split into simpler sentences: Martin returned for two episode's on 19 and 21 April 2011. His two episode return saw on 19 April, 10.31 million people watch and 8.43 million on 21 April.