Tom Shippey 
Beowulf and the North before the Vikings [PDF ebook] 

Ever since Tolkien s famous lecture in 1936, it has been generally accepted that the poem Beowulf is a fantasy, and of no use as a witness to real history. This book challenges that view, and argues that the poem provides a plausible, detailed, and consistent vision of pre-Viking history which is most unlikely to have been the poet s invention, and which has moreover received strong corroboration from archaeology in recent years. Using the poem as a starting point, historical, archaeological, and legendary sources are combined to form a picture of events in the North in the fifth and sixth centuries: at once a Dark and a Heroic Age, and the time of the formation of nations. Among other things, this helps answer two long-unasked questions: why did the Vikings come as such a shock? And what caused the previous 250 years of security from raiders from the sea?