Original: The two administratively independent unitary authorities, which were established on 1 April 1996 following the break up of the county of Avon, are North Somerset and Bath and North East Somerset.
Simplified: In 1996 Avon was split into 4 parts, which are now unitary authorities. People usually say that 2 of these parts (named North Somerset and Bath and North East Somerset) are part of Somerset, even though they have their own councils.