Essex Society for Archaeology & History
Note: I have used both ESAH and EASH interchangably - while this sounds dyslexic both acronyms are used. The proper designation is ESAH.
Information was found relating to Belchamp Walter Water mill and various other areas of Belchamp Walter's history.

The Brasses of Belchamp Walter

The Belchamps
The EASH have a good synopsis of how the Belchamps came into being and why they are named. Belchamp St. Paul's was so called as it was the "possession" of the Canons of St. Paul's in the city of London. Belchamp Walter and other locations around the area were "possessions" of the Abbey and Abbot of Edmundsbury (Bury St. Edmund's). Although not well documented there appears to be a rivalry between the two ecclesiastical entities.
The EASH account of the Belchamps also discusses the orgin of the parish names. Histories based on these accounts and those that cite Morant and Reaney seem to indicate a connection to Walter de Tey - I think that this is an arror. While it known that Walter de Tey is a relative of William de Beauchamp, by marriage, I think that the Walter part of the name of the village is more likely to have come from the de Beauchamp family.
The occurance of the de Tey connection in a number of earlier histories has been perpetuated by later historians. This has resulted in the notion that Belchamp Walter "held" the village in 1290. This period of time was around the Botetourt Years of Belchamp Walter's history. Sir John de Botetourt was married to a descendant of the de Beauchamp family evidenced by the de Beauchamp coat of arms found on the chantry chapel in St. Mary's church.