THERE is an almost complete absence of written records for the history of these islands between A.D. 400 and 550. Darkness hangs over them, and the mists of the Arthurian legend. In recent years the regional study of place-names, the excavation of dwellings, cemeteries, boundary and defensive earthworks, air- survey, and the efforts to establish reliable criteria for the dating of pottery, coins, and metal-work have accumulated material for a reconstruction of the course taken by various bands of invaders, the nature of their settlement, and the fate of the Romano-British population. A synthesis of such results may eventually enable some picture to be formed of these dim centuries. In the meantime certain controlling factors may be noticed.
The coast-line of England has altered considerably since early medieval days.1 The east and south coast, from the Firth of Forth to the Isle of Wight, presented at that time alternate stretches of cliffs and tidal marshes. The cliffs were easily defensible; only the gaps formed by river-mouths required to be guarded, and the remains of late Roman signal-stations and coast-fortresses show how this was effected. The marshy inlets, on the other hand, lay open to the boats of the invaders, with their shallow draught. The Humber estuary, stretching far inland, formed a huge waterlogged region, and similar conditions were repeated on a larger scale round the Wash, where the fen country extended as far as Stamford and Cambridge. 'For the plundering raider . . . the stagnant channels would float his vessel into the heart of the land, and on many an island in the swamps he could form camps in which to rest from fighting and collect his booty undisturbed.'2____________________