Complex sentence: The borough was merged with Blackburn in 1974 under the Local Government Act 1972, the town became part of the Lancashire non-metropolitan district of Blackburn, which was renamed Blackburn with Darwen in 1997, shortly before it became a unitary authority.
Split into simpler sentences: The borough was merged with Blackburn in 1974 under the Local Government Act 1972. The town became part of the Lancashire non-metropolitan district of Blackburn, which was renamed Blackburn with Darwen in 1997, shortly before it became a unitary authority.