What seems to be abundantly clear is that the export of tin from Britain had come to an end by the first century of the present era. Caesar, on invading Britain, heard nothing about it, and when Britain was finally conquered, the Romans who worked the lead mines in the Mendips, and gold and copper in Wales, totally neglected Cornwall, holding it to be worthless. They never settled there, only traversed it to the Land's End, leaving behind them a couple of square camps, some coins, few and far between, and some Samian ware; but this shows little more than that a traffic went on between the Britons of Cornwall and the Romans and Romano-British beyond Exeter. The fact that the Romans had no idea that tin was to be found in the peninsula shows that the mining for it had ceased there for some time previous. The Brythonic Celts are held to have invaded Britain b.c. 300; and it is probable that from that date the industry in tin mining carried on by the Ivernian natives declined rapidly and expired, leaving not a tradition behind.
It is noteworthy that the Dumnonii were behind the British peoples in the east. They had no coinage, whereas those in the south-east had theirs, copied from a stater of Philip of Macedon. No Greek coins had reached the Dumnonii, and they had consequently none to copy, however clumsily.
In the battle of Deorham, 577, the Britons were defeated with great slaughter, and the West Welsh of Devon and Cornwall were cut off from further communication with their brethren of Wales. The Saxons steadily advanced, but for long the Parrett was the boundary. In 823 a battle was fought between the Saxons and Britons at Gavulford, now Galford, a point on the old road from Exeter to the west, where the hills draw together, and whence it is commanded by a huge camp. The Britons now called the Danes to their aid, and twelve years afterwards a battle was fought on Hingeston Down, above Calstock, in which Egbert was victorious. This was in 835. Hitherto the Britons had occupied one portion of Exeter, but Athelstan, after defeating the Cornish King Howell, not only expelled them from the city but fixed the Tamar as their boundary. Then he passed through Cornwall, and even visited the Scilly Isles. The Count of Poher in Brittany, of whose son Alan Barbetorte was the godson of Athelstan, fled from Brittany with a crowd of his countrymen from the devastations of the Northmen, and Athelstan gave them homes in England. It is probable that he planted some in the Lizard, and others about Camborne, for we find there church dedications to distinctively Breton saints, and we know, moreover, that the fugitive Bretons brought with them the bones of their patron saints. As they spoke the same tongue as the Cornish, it would be natural for Athelstan to send them there.
In 981, the Danish pirates plundered the monastery of St Petrock, and in 997 ravaged the territories of their old allies from one end of Cornwall to the other with fire and sword. Shortly before this, in 993, Olaf Tryggvason of Norway, with Sweyn Forkbeard of Denmark, after having attacked London, devastated the east coast, burnt Sandwich and Ipswich, and stormed Bamborough, then harried the Scottish coast, the Western Isles, the Isle of Man, and Ireland, where "he burned far and wide, wherever inhabited." He then came to the Scilly Isles, where he put into Tresco harbour. There the monks of the abbey founded by Athelstan so impressed him, that he consented to be baptized.
In 1068, the county was plundered by Godwin and Edmund, sons of Harold, after a battle in Somersetshire, and on their way back to Ireland.
In 1322, the craze for going on pilgrimage took possession of Cornish men, women, and children, and they set off for the Holy Land, whence few returned.
In 1497, in consequence of the dissatisfaction occasioned by the levy of a burdensome tax, the commoners of Cornwall, headed by Thomas Flamank, a gentleman, and Michael Joseph, a Bodmin blacksmith, rose in rebellion. Having prevailed on Lord Audley to be their general, they marched as far as to Blackheath in Kent, where they were defeated with much slaughter by Lord Daubeny. In the same year Perkin Warbeck landed, according to some at Whitesand Bay, near the Land's End, according to others in St Ives' Bay, and marching to Bodmin, found the Cornish ripe for a new rebellion. At the head of 3000 men he marched to Exeter, but was unable to take it. He made his way to Taunton, where, despairing of success, he deserted his army and fled, but was taken and executed.
In 1548, another rebellion broke out occasioned by the changes in religion, which the Cornish resented. Their leader was Hugh Arundell, Governor of St Michael's Mount. They proceeded to besiege Exeter, but although the city was sorely distressed for want of provisions it held out till relieved, and in a battle fought at Woodbury, they were defeated with immense slaughter. Cornwall remained quiet in the reign of Elizabeth, save that it sent out whole fleets of privateers to prey on the Spanish traders and treasure vessels.
The Armada was off the Lizard on the 29th to 30th July, 1588. An English fishing-boat was hanging near them, counting their numbers. They gave chase, but the boat shot away down wind and disappeared. It carried the news to Drake at Plymouth, who at once prepared to sail forth.
In the Civil War, Cornwall was almost unanimous on the side of the King. Lord Robartes, however, threw in his lot with the Parliament. On the side of the King were Sir Bevil Grenville, Sir Ralph Hopton, Godolphin, Slanning, and Trevanion. A battle was fought at Boconnoc on January 19, 1643, in which General Ruthven and the Roundheads were defeated. Another battle in which the Royalists were successful was at Stamford Hill above Stratton, May 16, 1643.