Analysis of information sources in references of the Wikipedia article "London boroughs" in English language version.
The Municipal Corporations Act 1882 shall apply to every London borough
The municipal corporation of a borough shall [...] (a) in the case of a borough being a city, the mayor of which is entitled to bear the title of lord mayor, bear the name of the lord mayor, aldermen and citizens of the city; (b) in the case of any other borough being a city, bear the name of the mayor, aldermen and citizens of the city; and (c) in the case of any other borough, bear the name of the mayor,' aldermen and burgesses of the borough.