イングランドで最大の都市はどこ？
As noted above, in ordinary discourse, "city" can refer to any large settlement, with no fixed limit.
There are certain towns with large urban areas that could qualify for city status on the grounds of population size. Some have applied for city status and had the application turned down. Northampton is one of the most populous urban districts not to be a London Borough, metropolitan borough, unitary authority or city; on this basis, the council claims that it is the largest town in England.
Northampton