Complex sentence: The two administratively independent unitary authorities, which were established on 1 April 1996 following the breakup of the county of Avon, are North Somerset and Bath and North East Somerset, which were once part of Somerset before the creation of Avon in 1974.
Split into simpler sentences: The two administratively independent unitary authorities, which were established on 1 April 1996 following the breakup of the county of Avon, are North Somerset and Bath and North East Somerset. These unitary authorities include areas that were once part of Somerset before the creation of Avon in 1974.