bishops; but ultimately the Norwegian bishops, the first of whom was William the Old (consecrated in 1102), continued the canonical succession. The see remained vacant from 1580 to 1606, and from 1638 till the Restoration, and, after the accession of William III, the episcopacy was finally abolished (1697), although many of the clergy refused to conform. The topography of Orkney is wholly Norse, and the Norse tongue which evolved into the local Norn, at last extinguished by the constant influx of settlers from Scotland, lingered until the end of the 18th century. Readers of Scott's Pirate will remember the frank contempt which Magnus Troil expressed for the Scots, and his opinions probably accurately reflected the general Norse feeling on the subject. When the islands were given as security for the princess's dowry, there seems reason to believe that it was intended to redeem the pledge, because it was then stipulated that the Norse system of government and the law of Saint Olaf should continue to be observed in Orkney and Shetland. Thus the udal succession and mode of land tenure (that is, absolute freehold as distinguished from feudal tenure) lingered to some extent, and the remaining udallers held their lands and passed them on without written title. Twentieth century The islands cluster round the huge deep-water anchorage of Scapa Flow like a protecting hand, and in both World War I and World War II, the Royal Navy had a major base there, enabling them to challenge any attempt by German warships to emerge into the ocean through the Norwegian Sea. After the Armistice in 1918, the German High Seas Fleet was transferred in its entirety to Scapa Flow while a decision was to be made on its future; however, the German sailors opened their sea-cocks and scuttled all the ships. Most ships were salvaged, but the remaining wrecks are now a favoured haunt of recreational divers. Second World War One month into World War II, the Royal Navy battleship HMS Royal Oak was sunk by a German U-boat in Scapa Flow, with the loss of 835 lives. As a result, barriers were built to close most of the access channels; these had the additional advantage of creating causeways whereby travellers can go from island to island by road instead of being obliged to rely on boats. In the course of the Second World War Italian prisoners of war were kept