Complex sentence: After his contract had expired and was not renewed, Magilton left the club on 2 April 2012, and pursued legal action against the club, on the basis that he had been offered a three-year contract extension, that had then been rescinded.
Split into simpler sentences: After his contract had expired and was not renewed, Magilton left the club on 2 April 2012. He then attempted to pursue legal action against the club, on the basis that he had been offered a three-year contract extension, that had then been rescinded.