F. de P. Castells (1867–1935) is the main Masonic author on the subject of the Holy Royal Arch of Jerusalem, which is considered to be the completion of “pure ancient Masonry". Castells was a Protestant missionary born in Spain who was nationalised as a British citizen. He wrote books such as “Historical Analysis of the Holy Royal Arch”, “Antiquity of the Holy Royal”, “The genuine secrets in Freemasonry prior to A.D.1717” or “English Freemasonry in its period of transition (1600 – 1700)”.
