The smallest city in England is the City of London. It's only just over a square mile in size and, because it's mainly a business area, very few people live there:
http://www.cityoflondon.gov.uk/Corporation
(London itself isn't classed as a city, even though it contains two cities, the City of London and the City of Westminster).
things must be mighty dull in Nottingham if they have to resort to pinching Chris's bum! Clearly the ladies of Derby have their own local talent to fall back on.