Trematon is on the Lynher which, rising near Five Lanes towards the centre of the county, flows steadily south until it is joined by the Tidy near Ince Castle, (the only sixteenth-century brick house in the county), and with a sharp easterly turn flows broadly and genially into the Tamar below Saltash. Above its placid waters rises the old keep, the keep that was built to keep the unruly Cornish in order. Tintagel, Restormel, and Launceston are ruinous, but Trematon is still in fairly good repair. The wall crossing the motte is of early date, probably thirteenth century, while the archway of the square entrance tower carries portcullis grooves, and the keep, once 70 ft. by 50 ft., is still about 30 ft. in height. The castle with its park and manor and the borough of Saltash was granted by Edward III. to the Dukes of Cornwall for ever. It is not generally known that in some respects this dukedom differs from all others. The eldest son of the reigning sovereign is the duke, and he comes of age as soon as he is born and preserves all the rights of the dukedom without patent of creation; the essential difference between this and the princedom of Wales being that the latter is specially conferred by the sovereign.
Not far from Trematon is St. Germans, birthplace of the famous Sir John Eliot, after whom Port Eliot was called. This worthy, though consistently loyal to Charles I., opposed that monarch's illegalities and died in the prison to which he was consequently consigned. He was one of the noblest of the fine band of Cornishmen who came to the front at that period of the nation's history, an honest, just, and fearless man. Port Eliot, though charmingly situated where the Tidy widens into a lake, is otherwise only interesting on account of its pictures, of which there are several by Sir Joshua Reynolds.
St. Germans is thought to have been the seat of the ancient bishopric of Cornwall, but there is no evidence in support of the theory. The "see," or bishop-stool as it was called by our fathers, was nothing more than the seat of the bishop, the church in which it rested being his cathedral church. In early times the bishop was generally attached to some monastery or else he moved from place to place, taking his "seat" with him. In course of time, a suitable place being found, the see would become fixed, but there is no evidence of any fixed see in this county until 1877, when it was placed at Truro.