text: The earliest English record of the kingdom dates to Bede's , which noted the arrival of Bishop (later Saint) Mellitus in London in 604. Æthelberht (King of Kent and overlord of southern England according to Bede) was in a position to exercise some authority in Essex shortly after 604, when his intervention helped in the conversion of King Saebert of Essex (son of Sledd), his nephew, to Christianity. It was Æthelberht, and not Sæberht, who built and endowed St. Paul's in London, where St. Paul's Cathedral now stands. Bede describes Æthelberht as Sæberht's overlord. After the death of Saebert in AD 616, Mellitus was driven out and the kingdom reverted to paganism. This may have been the result of opposition to Kentish influence in Essex affairs rather than being specifically anti-Christian.
  The kingdom reconverted to Christianity under Sigeberht II the Good following a mission by St Cedd who established monasteries at Tilaburg (probably East Tilbury, but possibly West Tilbury) and Ithancester (almost certainly Bradwell-on-Sea). A royal tomb at Prittlewell was discovered and excavated in 2003. Finds included gold foil crosses, suggesting the occupant was Christian. If the occupant was a king, it was probably either Saebert or Sigeberht (murdered AD 653). It is, however, also possible that the occupant was not royal, but simply a wealthy and powerful individual whose identity has gone unrecorded.