Bastille Day, July 14, is a good day for an old order to come to a sudden and brutal end. And on July 14, the blade came down on the phenomenally successful “buy oil, sell financials” trade.

This trade, popular with hedge funds, offered a rare way to make money this year. It exploited the credit crisis and the response it provoked from the Federal Reserve. Investors deserted banks in the US (and Europe to a lesser extent) and bet that liquidity would instead flow to oil. As higher oil prices made it harder to aid banks with lower rates, and intensified pressure on banks’ customers, it was self-reinforcing.