Dr. David Harrison, a renowned Masonic historian based in the UK, was a featured guest on the Historical Light Masonic Podcast. With a PhD from the University of Liverpool, Dr. Harrison has authored several books and contributed articles to various magazines around the world, including the UK-based Freemasonry Today, the US-based Knight Templar Magazine, and the Australian-based New Dawn Magazine. His work has also been the subject of television and radio appearances. Dr. Harrison's research focuses on the origins and development of English Freemasonry, and he is a proponent of the 'river theory,' which suggests that Freemasonry originated from the Stonemason's Guilds in England and became influenced by various popular ideas throughout the seventeenth and eighteenth centuries. His first book, The Genesis of Freemasonry, was published by Lewis Masonic in 2009 and was followed by The Transformation of Freemasonry, which examines the society's evolution in the nineteenth century. In a TV interview, Dr. Harrison revealed that he is a Freemason himself.