Only last summer, the US Commodity Futures Trading Commission brushed off worries about speculators in energy markets like a lazy bovine would a cloud of flies. An altogether different beast appeared in this week’s hearings on how to curb speculation, called by its new chairman Gary Gensler. His tough talk is welcome – but matching it with action is harder.

Speculation – trading to profit from price movements rather than to transact physical goods – is not manipulation. But claiming that speculation has no effect on prices beggars belief. The share of physical hedgers in markets has shrunk as investors large and small have discovered commodities as an asset class. It is inconceivable that such change does not affect prices.