Last Wednesday night, David Clark, a London-based banker, received a nasty shock. Reports from Washington suggested the US government would soon impose restrictive new regulation on the derivatives world - a move Mr Clark believes could severely damage financial business in London and New York.

He duly prepared a furious statement on behalf of the Wholesale Market Brokers' Association, a lobbying group he leads. But when, a few hours later, he saw the proposals from Tim Geithner, US Treasury secretary, Mr Clark had second thoughts. "What Geithner has written may not be so bad," he says, adding there is now "uncertainty" about what will happen next.