Experienced parents are familiar with the situation. There is a happy silence and an absence of small children from the immediate area. One parent looks at the other and says: “Go see what they’re doing and tell them to stop it.”

In the same way, the US regulators and other authorities seem to be threatening the happy playtime of commodity-linked exchange traded products, which till very recently had been busily putting together new vehicles to offer investors exposure to oil, natural gas, agricultural commodities and the like.