Dr. David Harrison is probably the best-known contemporary British historian of Freemasonry. He received his PhD from the University of Liverpool in 2008, and his thesis was published the following year as The Genesis of Freemasonry. His other books include Rediscovered Rituals of English Freemasonry, The Rite of Seven Degrees, and The Lost Rites and Rituals of Freemasonry (published by Lewis-Masonic).
In this interview, Dr. Harrison discusses the 18th century Rites and Masonic mystics (such as Martinez de Pasqually, Louis-Claude de Saint-Martin, and Jean-Baptiste Willermoz) that paved the way for such secretive esoteric and occult Orders as the Hermetic Order of The Golden Dawn and the Ordo Templi Orientis.
You can check out Dr. Harrison’s website here.