It was a mild autumn mid-morning when Trish and I set out, breaking through the heavy layer of duckweed in our kayak, and heading for the channel to the Great Ouse. The sun shone sweetly, our coffee flasks awaited our attention at my feet, and the river lay before us. We have made this journey down to Cardington Lock at least a hundred times. We know every inch of each bank of the river – and it's precisely because we do that we notice what has changed. Six weeks ago, we were on the hunt for...