Well, since you did ask.
First a word about the data. The CfC gathers data on the 63 largest cities in Britain, from London (pop: 9.8m all the way down to Worthing (pop: 107,000). As to what counts as a university, we’re only counting the main campuses, not smaller branch campuses. Last but not least, we’re not counting the Open University, which is technically based in Milton Keynes, but as a distance learning institution doesn’t have a campus in the traditional sense
Before running the numbers on this I sort of assumed the answer would be Edinburgh (because it has six universities, but isn’t that big), or London (which is that big but has, as I may have mentioned, loads of universities).
This just goes to show why you should never trust to guesswork: even with 40 universities, London is so huge that it’s nowhere near the top of the “universities per head” league table. (It ranks 26th out of our 63 cities.)