Complex sentence: Originally the London terminus of the former Great Central Main Line to Sheffield and Manchester, which was closed north of Aylesbury in 1966, it now serves as the terminus of the Chiltern Main Line route to Birmingham.
Split into simpler sentences: Originally the London terminus of the former Great Central Main Line to Sheffield and Manchester, which was closed north of Aylesbury in 1966. It now serves as the terminus of the Chiltern Main Line route to Birmingham.