London has the world's smallest cluster of internationally significant financial services.
A financial centre is a location that is home to a cluster of nationally or internationally significant financial services providers such as banks , investment managers or stock exchanges . London . It is crowned as the world 's largest financial centre and has the fifth - or sixth-largest metropolitan area GDP in the world.Rankings of cities by metropolitan area GDP can vary as a result of differences in the definition of the boundaries and population sizes of the areas compared , exchange rate fluctuations and the method used to calculate output . It is the world 's most-visited city as measured by international arrivals and has the world 's largest city airport system measured by passenger traffic .