This confidence key is very much a guide and not a definitive statement. These classifications are not fixed and can and do change. An example would be Acton Bank in Shropshire which David J. Cathcath King rejected as a burial mound but which on a later aerial photograph clearly shows the crop mark of a bailey. It should also be born in mind that many authors, particularly older authorities like King, held a very military definition of the castle and some sites they rejected may actual fulfil other, less military definitions. This confidence guide is not a statement of how certain it is that a site existed but how certain it is that a site existed as a fortification or as otherwise described. The intent of Gatehouse is to record all sites that have ever been proposed as medieval fortifications including all those that have since been rejected.
It should be noted that David King's 'possible' sites, in Castellarium Anglicanum, tend to be closer to the questionable category in Gatehouse.
Gatehouse attempts to give some idea of the amount of visible remains. This information is based on second party site descriptions and may well be out of date or otherwise inaccurate. The remains categories are;
Gatehouse attempts to record the legal status of the sites recorded.
Scheduled monuments are those sites scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. These are often called Scheduled Ancient Monuments or SAMs although, since some scheduled sites may be of recent date, the 'Ancient' is omitted by careful users. For England the data in Gatehouse is derived from The National Heritage List for England and has a high degree of reliability. For Wales the data was derived from the CARN database, which is no longer freely available although the records are reasonable reliable. It should be noted that Gatehouse records the legal status of the given location so the scheduling record may not well not mention the medieval history or remains of the site. (A bastle built with a Roman mile fort on Hadrian's Wall is unlikely to be mentioned in the scheduling record.)
Listed buildings are those building listed under Planning (Listed Buildings and Conservation Areas) Act 1990 for special planning regulations under the three grades of:
Listed building are listed for their historical and architectural importance. Therefore listed building records often include something of the history of a location and because of this Gatehouse records listed buildings standing on the site of medieval building even if they don't have any apparent medieval remains.
For England the data in Gatehouse is derived from The National Heritage List for England and has a high degree of reliability. For Wales there is no available online record of listed buildings and the data was derived from mentions in other records such as Coflein and is, therefore, likely to be incomplete and may occasional be out of date or otherwise unreliable.
All Gatehouse records represent the state of available information at one particular time. Sites are investigated and reinterpreted, they change over time, get scheduled or descheduled, get added or removed from building lists etc.