City
Officially, the part about having a cathedral to be a city was done away with in the 19th century; the only criterion now is that the town has received a charter from the monarch making it a city.
Hence Taunton is a town; and the only city in Somerset is Wells, because it has had a cathedral for centuries, which gave it city status a long time ago. (Bath hasn't been in Somerset for some time; it's now within BANES).
An interesting point is that Rochester lost their city status because of re-organisation; and it took 4 years before they realised that.
http://www.bbc.co.uk/news/magazine-13841482
But to get back to the main point; probably not an "IT Problem" but a "Data problem". I.e., someone put the wrong data in the system, and it output a bogus result.
Biting the hand that feeds IT
