What is the difference between City of London police and London Metro police? (US resident, my only time in London was a quick drunken jaunt through SOHO on a long layover)
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.
It's "just" a business district within London, leaving aside a couple of millennia of history. London comprises the City and 32 boroughs, somewhat similarly to the way New York is made up of five boroughs, one of which is also called "New York" in some contexts.
Far and away the most stunning thing I saw when I visited London as a tourist in 1979 was the wall around The City of London. This is the ancient wall that at one point protected the city from attack. Why was it stunning? Because we walk up to the wall and look down a deep ditch of about twenty(?) feet to view the top of the wall. From the go go American point of view where things are transient and everything is new, to realize I was standing on the results of two thousand plus(?) years of human habitation, which had slowly raised the level of the earth all around that much, gave me a visceral sense of my connection with human history.
I would think it's the distinction between the "City of London" (just the city itself) and the "London Metropolitan Area" (the city and surrounding sprawl).
In fact the City of London is a tiny part of the city of London, and only one part of the centre (the north-east). It's the area that was originally defended by a wall in Roman times.
"The City" is a tiny little slice with something like one hundred residents. It bears zero relation to London, the London Urban Area, the London Metro Area, or the London Municipal Area.
City of London is the financial district, a city within a city. Most of the voters there are companies and it is administered by a corporation. Dick Whittington ran it for a bit with a cat that liked sturdy footwear. It is weird.
EDIT: Thank you all for informing me!