Complex sentence: By the early 1960s it was apparent that John Rennie's 1831 London Bridge was gradually sinking into the River Thames and Greater London Council decided that a new bridge would need to be built.
Split into simpler sentences: By the early 1960s it was apparent that John Rennie's 1831 London Bridge was gradually sinking into the River Thames. The London Council decided that a new bridge would need to be built.