Britain's National Consumer Council (NCC) recently ranked UK supermarket chains according to their environmental credentials. (Waitrose came top, Sainsbury's led the four largest chains.)

It’s not the first time the NCC has done this kind of exercise. But it must have had more of an impact in supermarket marketing departments than the report cards it produced a couple of years ago.

Over the last two years sustainability (or corporate responsibility) has become a competitive issue for Britain’s big grocers.