Tamar

The Tamar is remarkable in that it flows southwards from a source which is less than 4 miles (6 km) from the north Cornish coast. From near this point the Cornish border heads to the sea along Marsland Water[?], making Cornwall nearly an island. However, in a few places the administrative border deviates from the river, leaving, for instance, the Devon village of Bridgerule[?] on the 'Cornish' side. And for most of its length the river does not in fact form much of an obstacle to communication, there being some 20 road crossings.