On the edge of the Bayford Pinetum in rural Hertfordshire, in view of the surrounding farmland, there's a young birch tree, growing in a secluded hollow. In early September the foliage here was humming with late season bees, feeding on ivy. Now in late October, the land is rain sodden and the dell is flooded waist deep. Rooks caw and kaah, from high in the treetops. The air is alive with the watery sibilances of rushing winterbournes. Flocks of jackdaws tchack tchack over the claggy brown fields, ploughed over since our last visit. The occasional train slides smoothly through the forest, on the line that links Hertford North with London. Propeller planes hum over on their weekend flights. Jets pass, muffled in the cloud. High leaves rustle gently in the cool autumn breezes. They haven't got long to fall.