Long settled as mostly farmers in the lands their ancestors had invaded four centuries before, the Saxons were now called upon to repel another wave of invaders - the Vikings of Norway and Denmark. The raids had begun in the 8th century but by the middle of the 9th had become an invasion.

Danish Viking raids on Wessex occurred frequently from 835AD onwards and in 851 a huge Danish army arrived in the Thames estuary. However they were decisively crushed by Egbert's son and successor King Aethelwulf in the Battle of Aclea, which postponed Danish conquests in England for a few years although raids on Wessex did continue. In 865 another huge Danish army arrived in England, and in the following years the Danes over ran eastern England and Northumbria, and began to threaten the southwest.

In 871AD the Danes invaded Wessex, but were checked at Ashdown in the Berkshire Hills by Aethelred and Alfred of Wessex. The arrival of yet another Danish army compelled Alfred to pay the Danes to leave Wessex, but in 876 they returned before finally withdrawing in 877.

At the beginning of 878AD the Danes started a winter invasion of Wessex and took Alfred by surprise. They over-ran much of the kingdom and Alfred took refuge with a small band of followers in the marshes of Somerset, but some months later he was able to gather an army and defeat the Danes at the Battle of Edington which brought about their final withdrawal from Wessex. Forced to come to terms, they would retire behind the line of Watling Street, into the Danelaw, and also accept Christianity.

White Horse Hill, Oxfordshire

King Alfred the Great then turned his attention to reforming the administration of justice, rebuilding churches, founding schools for the sons of his noblemen including bringing over foreign scholars, and began the compilation of the English Chronicle. With assistance from his scholars, he himself translated several books from Latin into English including Bede's Ecclesiastical History, and to his version of Gregory's Cura Pastoralis he added a preface describing the decay of learning. When Alfred died in 900AD the later part of the 10th century had become something of a golden age due in a large part to his work. The West Saxon dialect of this period became the standard written form of Old English for the rest of the Anglo-Saxon period and beyond.

Æthelflæd (Aethelflaed), daughter of Alfred the Great, married Æthelred Ealdorman of Mercia and after his death in 911AD she ruled as ‘Lady of the Mercians’ until her death in 918. Meanwhile Alfred's son, Edward the Elder, was in possession of London, Oxford and their surrounding lands, which had been annexed from Mercia to Wessex. Between the years 913 to 918 Edward overwhelmed the Danes of Mercia and East Anglia, and brought all of England south of the Humber under his power. After Aethelflaed died Edward took over direct control of Mercia and in 927 Edward's successor, Athelstan, conquered Northumbria, bringing the whole of England under one ruler.

After the death of King Edred in 955, England was divided once more, with Edwig ruling in Wessex while Mercia passed to Edgar. However, when Edwig died in 959 the whole of England came under Edgar's control. When Ethelred II (The Unready) became king in 975/8AD the kingdom fell into confusion and in 980 the Danish renewed their attacks.

When Danish king Cnut came to power in 1016, he established earldoms based on the former kingdoms of Northumbria, Mercia and East Anglia, but initially administered Wessex himself. However a few years later he created an earldom of Wessex, which encompassed all of England south of the Thames, which was governed by Earl Godwin. Godwin and then his son Harold became the most powerful men in English politics after the king. After the death of Edward the Confessor in 1066, Harold was elected king by the Witan which reunited the earldom of Wessex with the crown. Harold would be the last Anglo-Saxon King of England.