Abstract The provenance of many objects once part of the acclaimed Revd William MacGregor collection of Egyptian artefacts is unclear or unknown. Private collectors purchased pieces from the MacGregor collection when it was sold at auction in 1922, many of which eventually made their way into major museums around the world. Today, the provenance information attached to them can usually be traced back through the private owners only as far as MacGregor’s ownership and no further. Recent research has revealed more about MacGregor’s collecting habits, including the fact that Count Riamo d’Hulst was the supplier of MacGregor’s famous obsidian head. Based on a little-known court case in Egypt and previously unseen correspondence between MacGregor and the Swiss archaeologist Édouard Naville, this article sheds further light on the extent to which the count was MacGregor’s regular supplier. It will also demonstrate how this key buyer–seller relationship developed, and how it eventually deteriorated into enmity and legal wrangling.