Cnut, or Canute, was King of England for nearly 20 years, dying in Dorset in 1035. A formidable figure, Cnut is one of the great 'what ifs' in English history. The culmination of a long period of Viking attacks and settlement across England, Cnut's reign could have permanently shifted 11th century England's orbit 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, Cnut created a Viking Empire at least as plausible as the Anglo-Norman Empire that would emerge in 1066.

Ryan Lavelle's book explores this fascinating and powerful man. He has popularly come down to us for the story of Canute and the waves - but he was a nation and empire builder on the grandest scale and his reign is a sort of masterclass in the contingent, wayward nature of history.