I thought there was something about the king of the UK having to ask permission to enter the City of London, but apparently that is a misunderstanding (https://en.wikipedia.org/wiki/City_of_London_Corporation#Tem...). Pity, it would have been a good story of even monarchy bowing to finance! =)
The Sovereign does have to ask permission to enter Parliament, however. It's observed in a ritual, twice-repeated refusal before every speech before Parliament.