The London Metropolitan Police (aka “Scotland Yard” although I don’t think anyone in London uses that term anymore) is the police force of Greater London, excluding the City of London which is basically the financial district of London (famously called the “Square Mile” for obvious reasons). It also has some nationwide responsibilities, such as counter-terrorism.

The City of London Police is the police force of the City of London only. Given that there are less than 8,000 people living in the City of London but more than 300,000 people work there (many of them very well paid), they specialise in white collar crime.