Complex sentence: She noticed the empty and derelict Sadler's Wells theatre in Rosebery Avenue, Islington, on the other side of London from the Old Vic, and decided to seek to run it in tandem with her existing theatre.
Split into simpler sentences: She noticed the empty and derelict Sadler's Wells theatre in Rosebery Avenue, Islington, on the other side of London from the Old Vic. She sought to run it in tandem with her existing theatre.