The Regent Diamond has long been celebrated as one of the most perfectly cut diamonds in history. Since its cutting around 1710, it has retained this distinction — a timeless testament to the exceptional craftsmanship of its cutter. Even by modern standards, few diamonds can rival the precision and beauty achieved in the Regent’s faceting.
Historical records note variations in the reported pavilion main culet angles, ranging from 41¾° (Tillander, 1966) to 45° (Morel, 1988; Bari, 2001). These differences have led to debate among gemologists seeking to understand the exact cutting geometry of this legendary diamond. However, because the Regent is permanently displayed at the Louvre Museum in Paris, direct measurements cannot be taken to confirm these details with absolute certainty.

Supporting materials exist in the form of lead casts of the rough stone and intermediate cutting stages, preserved in the Natural History Museum in London. Unfortunately, a cast of the finished gem has never been made, leaving researchers to rely on optical and photographic analysis.

Scott developed a method to infer pavilion angles by studying the reflections of the culet facet within the crown facets. This optical relationship directly correlates to the pavilion main angles — a subtle but powerful insight derived from the study of historical diamond cutting techniques. In comparative imaging, a pavilion angle of 41¾° positions the culet reflection differently than one of 45°, allowing accurate reconstruction of the diamond’s geometry within a margin of approximately 0.5°.