You know Main Avenue at the Chelsea Flower Show? That elegant thoroughfare between the biggest, most glamorous show gardens of the lot?

Not much glamour involved today. Somewhere to the left, behind a dumper truck offloading topsoil over the roots of a pleached hornbeam hedge, is Jo Thompson’s Stop the Spread garden, a far more beautiful and gentle sunken garden of natural planting than its publicity of dire warnings about ash dieback would suggest.

But you’ll have to take my word for that. Walking down Main Avenue today is like negotiating a particularly bad traffic jam on the M25, except you’re on foot and the vehicles are twice the normal size and prone to veering off to the side, or backwards, as whimsy takes them. I’m told it can take a dumper truck 45 minutes to move 250m in this lot. Doesn’t surprise me one bit.