Following the end of Roman control in the early years of the 5th century Essex was in the first phase of Saxon conquest. The newcomers rapidly acquired estates, which became parts of small territories. A unified East Saxon Kingdom probably emerged in the late 6th century (500-600 AD) out of a series of smaller territories such as the Rodings and Dengie. In the seventh century the kingdom probably extended as far as Middlesex and Surrey. Around 700, Middlesex, Surrey and London were lost to the neighbouring kingdom of Mercia, and though Essex itself appears to have been subject to limited Mercian overlordship thereafter, it remained an independent kingdom until around 820 when it was incorporated into Wessex.
The kingdom would have been administered through a series of royal vills, the location of some of which can be postulated through documentary, place name and archaeological evidence. The distribution of the known sites shows a correlation with major Roman sites, and we can imagine that at least some of the communications network represented by the Roman roads must have survived, and in Central and Northern Essex also bears correlation with the position of early Saxon cemeteries. This may represent some form of legitimisation, with the new Saxon elite attempting to justify their position by linking themselves to historical sites and specifically high status and important sites.