More of a lake than an ocean in the canon of the earth’s raging deeps, the North Sea is small, grey and shallow. To Bede on the banks of the Tyne at Jarrow in the eighth century it was a well of the unexpected, most of it unwelcome. Farther south on the low, hazy shores of “holy” Suffolk a snake’s head prow on the horizon perhaps bespoke Leviathan, in this instance a Viking longship. The newcomers who unsettled the Romans came by water. Not only at sea but along the network of mighty rivers draining into the Sea’s south-east corner or into its inner lake, the Baltic. How else could a statue of the Buddha arrive on a Swedish farm within a few years of his death? These people brought a vigorous hand to the desperate exigencies of existence. It is their achievem