The following is a list of licences to crenellate, surviving in the records, issued from the 12th to 16th centuries, which was compiled by the amateur historian Philip Davis and published in the Castle Studies Group Journal.
[1] A few supposed licences sometimes quoted in other sources were questioned by Davis as dubious, deemed forgeries or were rejected entirely, but were still included in his list suitably qualified.
The ultimate source for the licences is the patent rolls, the contemporary chronological official records made of all letters patent issued by English monarchs, and published in modern times as "calendars of the patent rolls preserved in the Public Record Office".