The city has undergone many changes to its governance over the centuries and once again became administratively independent from Hampshire County as it was made into a <answer>unitary authority</answer> in a local government reorganisation on 1 April 1997, a result of the 1992 Local Government Act. The district remains part of the Hampshire ceremonial county.
What official designation did Southampton receive in the April 1997 local government reorganization?
unitary authority