Complex sentence: In 1974, under the Local Government Act 1972, Southend became a district of Essex with borough status, however in 1998 it again became the single tier of local government when it became a unitary authority.
Split into simpler sentences: In 1974, under the Local Government Act 1972, Southend became a district of Essex with borough status. However in 1998 it again became the single tier of local government when it became a unitary authority.