Our `Regis' was undoubtedly added as a result of the manor having been Crown property from Saxon times until 1259, during which time it literally "belonged to a king".
During this period the reigning monarch was Lord of the Manor, and as such could freely take up residence at any time if he might so choose; and as King John took advantage of this on at least 16 occasions, this could be regarded as an additional reason for the `Regis' suffix.
On the other hand Bere was by no means the only royal manor; there were 30 in Dorset alone, and King John is known to have visited at least 21 of them, some, as in the case of Gillingham, Corfe Castle and Cranborne, more frequently than Bere, and yet they did not acquire a `Regis' suffix.
Moreover, Bere does not appear to have gained its `Regis' or `Kings' component until some time after King John's reign (1199-1216). During this period it appears as Bere or, in formal documents, in its latinised form Bera or Beram, and even in 1274, nearly sixty years after the end of John's reign it still appears as Bere.
However, in 1303 the anglicised form Kingsbere occurs, and seems to have remained in general use until the 16th century when both latinised and anglicised forms were in use, e.g. Beare Regis (1552) and Kynges Bere (1587).
During the 17th and 18th centuries, a period well covered by parish documents, it remained consistently as Beere Regis, but by the beginning of the 19th century this had become Beer Regis in which farm it appeared in trade directories and other official printed sources, until at least 1842.
The Post Office Directory of 1846 gives the spelling as "Bere Regis or Beer Regis", and these alternatives continued to appear in the directories until 1907.