I've just stumbled across a map by Mathew Paris (c.1200 - 1259). It's available in WikiCommons here:
https://upload.wikimedia.org/wikipedia/commons/4/44/Britannienkarte_des_Matthew_Paris.jpgMagnify, and scroll to the bottom and Kent is recognisable. The Thames discharges just north of the island labelled "Thanet", above that you can see "Sephe" (Sheppey). The Medway is shown with the main stream along the Swale and a minor branch joining the Thames. At the time this would acurately reflect the navigation. "Rofa" (Rochester) is visible with its castle, as are "cantuar" and "Doua", (Canterbury and Dover). Elsewhere theere is much that is recognisable, but this is the Kent forum so I'll stop there.
