Complex sentence: The British had their first taste of "Giselle" with a drama based on the ballet called "Giselle, or The Phantom Night Dancers" by William Moncrieff, who had seen the ballet in Paris the same year.
Split into simpler sentences: The British had their first taste of "Giselle" with a drama based on the ballet called "Giselle, or The Phantom Night Dancers" by William Moncrieff. He had seen the ballet in Paris the same year.