In those days north Kent was divided by open waters and marshes stretching inland. The safest navigation to the open sea was then the route from the Thames into the Yantlet Creek (separating the Isle of Grain from the rest of Hoo Peninsula), and thus into the Swale from the Medway estuary, around the leeward side of the Isle of Sheppey into the Wantsum Channel, navigating past the Isle of Thanet to Sandwich and only then into the open waters of the English Channel. It was thus an easily defensible planned-town centre for the wool trade.