After an overnight flight from Chicago's O'Hare Airport I arrived back at Heathrow at 7.30am, though to me it seemed like 1.30am as my body clock was still on Chicago time.

During the morning of my last day in the city I visited the Art Institute with its wonderful selection of paintings, and I observed a huge demonstration for World Earth Day in support of climate change and science.

There were lots of placards with Trump-related messages, such as 'Science trumps....' and one that said 'What do atoms and Trump have in common? They make up everything.'

There aren't many nations of the world where you can insult the head of state so freely and publicly, but you can in America. Watching over it all was this: