I want to make the most money possible - LONDON/HK

Your balance would be between the nominal income, the ceiling of your income, and the respective tax rates/living costs applied.

Broadly speaking and with little to no real data whatsoever, the potential ceiling of your income in London is higher than Hong Kong due to the trans-atlantic dealflow and broader base of economies you serve (all member states of the European Union). Also factor in the possibility of China's economy not recovering in the medium/long term, though that is not to say the Eurozone is doing much better.

However, the tax rates in the UK are also significantly higher than Hong Kong, which is known to be one of the most tax-friendly places to middle/high income but not asset-wealthy people in the world. London is heavily asset-owner friendly and conversely pure-income unfriendly, even more so than Hong Kong despite the latter's already high living costs, in my opinion, having lived in both across the span of >10 years.

From a somewhat vague view of the immigratory aftermath of the British colonisation of Hong Kong, I would assume you either hold the British National Overseas or, even better, outright British Citizenship (do NOT tell us). Signing up to the BNO visa would save employers a lot less hassle and put you into the pile which does not need visa sponsorship for it places you onto the track for British Citizenship. I had a friend who was rejected from a mid-market bank in London (think SocGen, BNY, Mizuho) after all interviews and assessments because they didn't want to sponsor the candidate, but had he/she signed up to the BNO visa, they would have let him/her in. But the tradeoff is your friends and family, daily life, and overarchingly whether you are willing to spend the next five years of your life living in the UK.

If studying at King's is your first time quasi-living in London, do give it due consideration about the lifestyle differences. I say quasi because living in London as a student and employee is vastly different. The social circles you had in university would be restructured once you enter employment - you won't be going to lectures at the same time, joining the same clubs and societies, doing the same sports, getting pints after class...etc. So do ask yourself, and only yourself, whether you like (or can put up with) living in London to achieve what you want. It is entirely fine if you cannot - Hong Kong is a great place for day to day living if you don't care about certain, now unspeakable, aspects.

Best of luck.