Find out more about the English Castle Award (ECA) programme here: https://englishcastlesawards.uk/
The ECA programme is part of the World Castle Award (WCA) here: http://wcagroup.org/
Google Earth KMZ layers showing the English Castle references and 1000m activation zones can be downloaded from this ECA page along with a Google Maps version also: https://englishcastlesawards.uk/reference-map/
Note how activation zones overlap so it is possible to activate multiple castle reference from a single operating site.
Thanks to Bob M0MJA for his management of the ECA programme.