The billboard was from the Bank of China. It said: "RMB: New Choice; The World Currency"

Given that the Bank of China is more than 70% owned by the government of the People's Republic of China, I find this very significant.

It means that China is literally advertising its currency overseas, and it's making sure that everyone landing at one of the world's busiest airports sees it. They know that the future belongs to them and they're flaunting it.

And it's true. The renminbi's importance in global trade and as a reserve currency is increasing exponentially, with renminbi trading hubs popping up all over the world, from Singapore to London to Geneva to Frankfurt to Toronto.

Multinational companies such as McDonald's are now issuing bonds in renminbi, and even sovereign governments are issuing debt denominated in renminbi, including the UK.