Until the ‘green revolution’ and the wholesale application of nitrogen fertilisers, the fertility to grow all arable crops was built by the kind of lush clover grass rotation I’m looking at. Holden, a bit of a superstar in the green movement (ex-head of the Soil Association and now head ofSustainable Food Trust), does a calculation in his head, quickly totting up the years: ‘So this has been in rotation six times,’ he says. Despite the day job, he has farmed this land continuously for 41 years. A day job, he says, is now key to maintaining small scale dairy farming, thanks to skewed economics.