The great grey river stretched into the horizon. The sun was big and low in the sky. The air was very fresh and the clear sky streaked with smears of pink and orange. We had only a little left of the day.

From our spot on the Globian Sluice, a steel grating promontory, we could see the gaunt cranes of DP World London Gateway port, smoking factories across the water on the Isle of Grain and a ship or two, loitering.