Complex sentence: The Borough Council was controlled by the Conservative Party from 1965 to 1986, when a short-lived SDP-Liberal Alliance minority administration took over, it lost several by-elections due to its attempt to abolish the Borough's grammar school system.
Split into simpler sentences: The Borough Council was controlled by the Conservative Party from 1965 to 1986, when a short-lived SDP-Liberal Alliance minority administration took over. It lost several by-elections due to its attempt to abolish the Borough's grammar school system.