Cnut, or Canute, is one of the great 'what ifs' of English history. The Dane who became King of England after a long period of Viking attacks and settlement, his reign could have permanently shifted eleventh-century England's rule to Scandinavia. Stretching his authority across the North Sea to become king of Denmark and Norway, and with close links to Ireland and an overlordship of Scotland, this formidable figure created a Viking Empire at least as plausible as the Anglo-Norman Empire that would emerge in 1066.

Ryan Lavelle's illuminating book cuts through myths and misconceptions to explore this fascinating and powerful man in detail. Cnut is most popularly known now for the story of the king who tried to command the waves, relegated to a bit part in the medieval story, but as this biography shows, he was a conqueror, political player, law maker and empire builder on the grandest scale, one whose reign tells us much about the contingent nature of history.