Complex sentence: By 1941 Drummond had qualified as a Panamanian chief engineer, as these examinations were a purely written paper, with the gender or status of the candidate not being known to the examiners.
Split into simpler sentences: By 1941 Drummond had qualified as a Panamanian chief engineer. These examinations were a purely written paper, with the gender or status of the candidate not being known to the examiners.