Preston soon began an extensive program of masonic research. Interviewing where he could, and entering into an extensive correspondence with Freemasons in Britain and overseas, he built a vast storehouse of masonic knowledge, which he applied initially to explaining and organising the lectures attached to the three degrees of Freemasonry. He met with friends once or twice a week to test and refine his presentation, and on 21 May 1772 he organised a Gala at the Crown and Anchor in the Strand at his own considerable expense, to introduce the Grand Officers and other prominent masons to his system. The success of his oration on that day led to the publication, later that year, of his "Illustrations of Masonry", which ran to twelve English editions in the authors lifetime, as well as being translated into other languages. In 1774 he organised his material into lecture courses, delivered by him at the Mitre Tavern, Fleet Street. There were twelve lectures per degree, at one guinea per degree.