A timeline by Willster22.
Since 867 and the coming of the Great Heathen Army, there has been a Viking presence in England. However, after the death of King Ethelred at the Battle of Merton and the succession of his brother Alfred, later known as "the Great", the Anglo-Saxons started to fight back the Vikings to a degree. In 878, which in OTL was the year when Danelaw was established after the defeat of the Vikings under Guthrum the Old by the Anglo-Saxons under Alfred the Great. But earlier the year, before the Battle of Ethandun, a Viking raid by Guthrum the Old upon Cippanhamm, known today in OTL as Chippenham, a winter castle of King Alfred's. During that raid, Alfred escaped capture and lived to see another day and defeat Guthrum and force his baptism after the battle of Ethandun. However, what if Alfred had been killed during that raid and been succeeded by his infant son, Edward, and the Vikings, under Guthrum and Halfdan. The Vikings in OTL had changed the history of England to a fair degree, but if they had taken a more permanent place upon the British Isles and there had been a more complete fusion and Anglo-Saxon and Norse cutlures, the world as we know it would be quite different indeed.