With Ronald M. Burrows, they undertook important excavations at Rhitsona in Boeotia, Greece.
[5] Percy has been described as "an inveterate picker-up of fragments"[6] which he acquired wherever he could, including from children or discarded under bushes at archaeological sites like Rhitsona or Mycenae.
Percy collected plain and functional items neglected by other scholars, believing that they might be as informative as more attractive pieces.
They wrote several important books on finds at Rhitsona as well as over fifty articles on Greek pottery.
In 1954 they produced an important volume in the international series, Corpus Vasorum Antiquorum, which covered about half of the current Ure Museum collection.