The British Pound.

Until the end of World War II, the pound was the currency of reference. The currency is heavily traded against the euro and the U.S. dollar, but has a spotty presence against other currencies. Prior to the introduction of the euro, both the pound benefited from any doubts about the currency convergence. After the introduction of the euro, Bank of England is attempting to bring the high U.K. rates closer to the lower rates in the euro zone. The pound could join the euro in the early 2000s, provided that the U.K. referendum is positive.