The last time such a large amount of gold crossed the Atlantic, the French were repatriating their gold reserves from New York in the 1960s, a few years before the gold-based Bretton Woods monetary system collapsed. The time before that, in July 1940, Operation Fish saw the British take 1,500 metric tons to Canada to keep the treasure away from Hitler in case he took London.
The armies approaching London these days are of a different kind: they wear bankers' suits instead of military uniforms, and their appetite for the gold in the vaults is no less strong. Some 500 tons of gold bars have returned to the New World, having flown to the vaults of the Comex commodity exchange in New York in recent days and weeks; most come directly from London or have stopped at refineries in Switzerland and elsewhere (to be melted down to Comex's exact specifications: 100-ounce bars versus London's 400-ounce bars).
Robert Armstrong of the Financial Times aptly voices the confusion (italics in the original): “...the gold is then flown to New York (Planes! To settle a financial transaction! In the 21st century!).”
It is understandable that some logistical problems have arisen. The Bank of England reported at its Monetary Policy Committee press conference on February 6 that all of its gold delivery spaces are saturated for weeks. Dave Ramsden, deputy governor of the Bank, put it bluntly: “It's an obvious point, but, you know, gold is a physical asset. Therefore, there are real logistical and security constraints.”
Gold has been the backbone of the global monetary and financial system for centuries, obviously under the various gold standards (classical, interwar, Bretton Woods), but no less important during the last fifty-odd years of pure fiat money. Central banks have mostly held on to the gold of past centuries; in recent years, some of them (Poland, Russia, China, India) have acquired considerable amounts. (The World Gold Council now routinely reports that central banks are buying more than 1,000 tons a year.)