The City of London is a sprawling beast. Yet when politicians and analysts talk about it, they tend to focus mainly on a narrow slice of it all – the banks. The  issue  of bank passporting has been pored over ad nauseam by commentators and officials, in huge disproportion to the size of the business that relies on it. But even as we’re obsessing about banks, we’re overlooking potentially much larger issues relating to London’s prominence in asset management.