1066 sticks in popular history because the effects of the Norman Conquest were so widespread and long-lasting compared to anything that came before it. The 'unification' under Æthelstan in 926-7 is really just the officialising of a de facto state of affairs which had begun in 919 when Edward the Elder of Wessex had deposed his neice Ælfwynn of Mercia in a coup and essentially unified the kingdoms. This in turn was the culmination of a steady process of alliance and unification which had been underway since the 830s.

The key factor is that, while very important, neither the events of 926 or 954 have an overwhelming effect on the administration, organisation or daily life of much of England. Both Mercia and Northumbria retain a surprising amount of political autonomy within the new English kingdom, regional elites retain their lands and privileges, and the Church remains essentially unchanged. In fact, Æthelflæd of Mercia is famed for restoring and promoting old Mercian regional saints' cults during her reign in a targeted act of nationalist propaganda.

A more comparable event to 1066 is the capture of England in 1016 which culminates in Cnut becoming King of England. This does effect the organisation and heirarchies of England to quite an extent - the fyrd system is greatly affected for example, and a prominent Anglo-Scandinavian nobility arises in some areas - but Cnut also tries hard to be an Anglo-Saxon king: He marries Emma, the former wife of Æthelred II, he ensures a continuity of currency, he leaves the legal structure largely unchanged and he patronises the English church. In particular he organises the restoration and refurbishment of the Cerdicing royal church of St Cuthburga's in the royal vil of Wimborne, Dorset, with an apology for the raiding his army had carried out there during the invasion.

1066 on the other hand is a vast and widespread upheaval that affects almost every facet of England. A lot of this upheaval can be seen via The Domesday Book and in surviving legal codes. Unlike in previous unifications or conquests, 1066 almost wipes out the English nobility. By 1086 almost all of the land-owners in England, as well as the vast majority of senior clergy, are Norman or Anglo-Norman. Land tenure is a major legal change as well: vast areas are incorporated into the Royal Demesne and all land is now held from the king rather than owned outright. The legal system undergoes a vast overhaul as well, and longstanding English systems such as weregild are largely abolished and replaced by a series of corporal punishments largely based around mutilation, as well as a general curtailment of the rights of women. The introduction of the vastly unpopular 'Forest Laws' also curtails the long-standing rights of the English to go hunting, and transforms this largely into an elite pursuit. The Normans also greatly overhaul the Church, moving and abolishing some bishoprics, abolishing the worship of some local saints, and building vast new cathedrals and churches. The arrival of castles and the concommitant restructuring of military power and centres of authority is also a long-lasting change still visible in the landscape.