What began as the construction of a trench for a water main became a ten-year long excavation. A few pieces of Roman pottery and tiles had been discovered in the early nineteenth century and in the early 1930s a mosaic was even discovered, but at this time it was inconceivable for people to believe that all of these elements would relate to one large building. Though there were many other discoveries prior to the finding of the red tiles, this one caught the attention of archaeologists and launched the excavations.

Instructed by a local archaeologist to be informed of anything that came up, a workman employed by the City of Portsmouth Water Authority expected nothing out of the ordinary. When the construction for a water main began, the operator of the machine noticed that he was cutting through masses of ancient building rubble and mentioned it to the engineer in charge who, after examining the pieces, reported it to the local archaeological committee.