Complex sentence: The London Underground 1967 Stock was a fleet of deep-level tube stock which operated on the Victoria line from when the line first opened on 1 September 1968 until 30 June 2011.
Split into simpler sentences: The London Underground 1967 Stock was a fleet of deep-level tube stock which operated on the Victoria line. The stock was used between when the line first opened on 1 September 1968 and 30 June 2011.