Martin Folkes (1690–1754) was Newton's protégé, an English antiquary, mathematician, numismatist and astronomer who would in the latter part of his career become simultaneously president of the Royal Society and of the Society of Antiquaries. Folkes took a Grand Tour from March 1733 to September 1735, recording the Italian leg of his journey from Padua to Rome in his journal. This paper examines Folkes's travel diary to analyse his Freemasonry, his intellectual development as a Newtonian and his scientific peregrination. It shows how, in this latter area, how he used metrology to understand not only the aesthetics but also the engineering principles of antique buildings and artefacts, as well as their context and place in the Italian landscape. Using Folkes's diary, his account book of his journey in the Norwich archives, and his correspondence with other natural philosophers such as Francesco Algarotti (1712–1764), Anders Celsius (1701–1744) and Abbé Antonio Schinella Conti (1667–1749), this paper will also demonstrate to what extent Folkes's journey established his reputation as an international broker of Newtonianism, as well as the overall primacy of English scientific instrumentation to Italian virtuosi.