Heathrow opened in 1946, Haneda opened in 1931, so actually Haneda is older. But when Narita opened in 1978 as a new international airport, Haneda became domestic flight only. In 2010 Terminal 2 is opened for international flights, and newest Terminal 3 opened in 2020. Most of foreign company flights use Terminal 3, so you were at the newest part of the airport. Haneda has been considered as world's top airport for cleanliness and accessibility. I visited there several times when I was little (almost 50-60 years ago!), Haneda was just normal airport. I remember people used to go outside and use boarding stairs to get onboard the airplane, and we get to see them off or welcome them back from the rooftop observation area.