After 1997 Hong Kong was return back to China, and British was borrowing Hong Kong for 100 years. During that moment, there are immigration law for new territory people, therefore there are a lot of Hong Kong people immigrated to British.
When I was passing the custom in the airport, the custom ask a lot of question about why will I visit London, compare with the other countries I visited, United Kingdom is similar as America, they are very careful about the visitor.
I took the train to the downtown area, the train schedule is around an hour. It is not that busy compare with the other cities. The pathform is quite similar as Hong Kong but internal is a little old. A beggar asked me for money inside the train. I just gave him some spare money and he gone.