The treacherous Wellstream estuary, where King John lost his baggage train on 12 Oct 1216. John came from Lynn, off to the right of the map, and had to cross the estuary from east to west, i.e. from right to left on the map. But we don't know which route he took. He was at Swineshead that night. My calculated search area is highlighted in red. The density of the red dots reflects the relative probability of finding something in that area.