In the year 834, Dorestad, the wealthy emporium at the fork of the Rhine about one hundred kilometres from the Dutch coast, was attacked and burnt, apparently by a force from Denmark. It was an astonishing move—this was no monastery or isolated community, but one of the most important places in the trading networks of northern Europe. This would be like physically assaulting one of today’s great financial hubs. The Vikings slaughtered at will and took shiploads of slaves. The surrounding region was devastated. The same was to happen every single summer for the next four years,
