On late afternoons in March, especially when there is a patchy sun glinting from the west, parts of the Vale of Aylesbury in Buckinghamshire are suffused with an orange glow. All over the floodplain, by dykes and lanes and thin streams, rows of gnarled pollards, many with a decided slant to their trunks, seem to have been coated in amber. Closer to, the sprays of twigs seem kaleidoscopic. They have ochre bark, ginger-shellaced buds, and the germs of what will soon be voluptuous crimson male catkins.