Looking over . . .

Northampton.
       Not yet a City . . . next year who knows?!

Traditionally, a city in the England & Wales was defined by the presence of  a diocesan cathedral. As with so many other things, that has changed and the bar for criteria has risen to include:

- population size and importance;
- having a distinctive character & identity;
- curiously, competitions for the granting of new city status can be held to mark special events, eg coronations, royal jubilees or the Millennium.

If Northampton were to play to its own historic strengths, I suspect it would be an even stronger candidate than before.

Interestingly, though London contains 2 cities (City of London and City of Westminster) it is not itself a city because of its lack of "letters patent."