The National Archives (TNA)
Kew, Richmond, Surrey, TW9 4DU
Hold the originals of many documents that have been utilised in developing this site.
Generally, File References have not been quoted but the Catalogues can be searched here.
And, almost certainly, you will find material that I have either not yet edited or uploaded. Do please let me know if you turn up anything really exciting!
I am a regular visitor to Kew.