Sporadic smog and frequent blue skies. This is London today. 50 years ago it was the other way around. As we circled above London in the busy morning air traffic, I thought of the generations of Londoners between the ramp-up of the Industrial Revolution in the 19th century and 1960s when the Clean Air Act began to take visible effect. These people did not see much of a sun unless they found their way out of the city. In 1952 during the Great Smog, thousands of people died and thousands more were made ill by the toxic filthy pea soup that hung over London for 4 days.
Today there is the chance to see a blue sky over London, even without rising a kilometer into the air. Of course the view from up here is much more stunning.