By Nicholas Wapshott
The opinions expressed are his own.

In medieval times, a key member of a monarch’s retinue was the food taster, a hapless fellow who ate what his master was about to eat. If the taster survived, the food was deemed safe for the king’s consumption. President Obama has a taster of sorts in David Cameron, the British prime minister, who has embarked upon an economic experiment that echoes the recipe of wholesale public spending cuts and tax hikes needed if both sides in Congress are to agree to raising the federal government debt ceiling. How the British economy is faring offers Obama an idea of what a similarly radical policy of cutting and taxing here would mean to the American economy.