Complex sentence: Before the extension, the Jubilee line terminated at; because the extension diverges east of, the section between Charing Cross and Green Park is now unused for passenger services but is maintained for emergency use.
Split into simpler sentences: Before the extension, the Jubilee line terminated at. The section between Charing Cross and Green Park, located after the rail junction east of Green Park, is now unused for passenger services but is maintained for emergency use.