King George VI was the spare—not the heir. Quiet and struggling with a speech impediment, few thought he had king potential.

As of 0817 GMT, the blue-chip index FTSE 100 fell 0.1% and the British GBP/USD slipped 0.07% against the dollar to 1.32. DAX index in Germany and the CAC 40 in France dropped 0.4% each.

One viral video can dominate conversations for weeks. That’s the power of social media-it turns moments into movements ...