In the days of our first Norman kings, a single square tower or keep, usually situated on a hill surrounded by an artificial ditch or moat, was considered sufficient protection. One might give a long list of such towers or keeps both in England and Normandy, for William the First, not content with overawing the Londoners with his great tower in their city, built others at Dover and at Exeter, at Nottingham and at York, at Lincoln and at Durham, at Cambridge and at Huntingdon. Under Duke Rollo and his immediate successors the Normans built their fortresses by the side of navigable rivers, on islands, or near the sea, since these fortresses were not merely destined as defences, but also for places of safety. They were, in fact, places of refuge for the people of the surrounding country, who fled to them with all their possessions, and particularly their live stock, at the approach of an enemy. By their situation, safety, if necessary, could be obtained by taking flight on the neighbouring river or sea. In Normandy—at Fécamp, at Eu, at Bayeux, at Jumiége, and at Oisel, to name but a few of these Norman keeps—this custom obtained. At Rouen, as in London, the principal fortress built by the Norman duke stood by the riverside, and not on the hills at the back of the town. None of these places mentioned above were stronger or more imposing than the great Norman keep in London, known for centuries as the White Tower, receiving that title at first, probably from the whiteness of its stone, and in later times from the continued coatings of whitewash which it received. Of the many castles in Normandy and Touraine of the same period as the White Tower, that of Loches resembles it most nearly in size and form. Loches is now almost a ruin, as are most of the Conqueror’s castles, but the great White Tower remains intact despite the storms, sieges, and fires through which it has passed during eight centuries. It is still the Arx Palatina of London and of the British Empire. Although in situation the Tower cannot compare with such grandly-placed castles as Dover or Bamborough, Conway or Carnarvon, or vie in beauty of scenery with Warwick or Windsor, it remains the most historic building in our land; not even the mausoleum fortress of Hadrian in old Rome can compete in interest with the Norman fortress—palace—and State prison of London; Edinburgh Castle alone approaches it as regards its influence on the history of the capital it defended, for the northern fortress was also the home of its national sovereigns for centuries, its country’s chief prison, the store-house of its regalia, and its city’s strong place of defence; and, like the Tower, it has been guarded from its foundation up to the present time without a break, by its country’s armed defenders.