The 33 divisions of the London Urban Area - City of London (officially not a borough), City of Westminster, Kensington and Chelsea, Hammersmith and Fulham, Wandsworth, Lambeth, Southwark, Tower...
The Largest of the London boroughs is the southern borough of Bromley, occupying 158,8 km2 (59 square miles). (http://en.wikipedia.org/wiki/London_Borough_of_Bromley).