Improved gas supply reveals Roman villa

In 2017, the National Grid carried out work to re-lay a gas main running through Verulamium Park. This involves running new pipes inside the existing pipeline and so has mostly required only re-excavation of sections of existing trench. However, small extensions were required to two holes, providing a rare opportunity to examine what lies underground in areas of the Roman town normally not accessible to hand digging, as the site is scheduled to protect it from damage.

Wealthy town house

The reopened trench section close to the Inn on the Park has provided evidence for a wealthy town house. The backfill of the original gas main included evidence for a mosaic. In addition, a series of floors were observed on either side of the gas main. One of these may have been an Opus Signinum floor made up of broken tiles and mortar. The final phase of this masonry building appears to have been some time in the third century AD, based on preliminary dating of the recovered pottery from the floor surface. However, there is evidence from above the floors that that the very last phases were associated with a much cruder form of architecture, the dating of which may have continued for some time afterwards.

Corner of city wall

A trench close to the London Gate has exposed the corner of the city wall. At this point there was no evidence of a tower as may have been expected. The absence of a corner tower is significant as it probably indicates that the city walls were built as much for show as for defensive purposes.

SAHAAS-aided magnometry survey

These discoveries follow on from Kris Lockyear of UCL’s magnetometry survey of the park conducted with the aid of members of SAHAAS and other volunteers from 2013 onwards. Those of you who have seen the survey results will remember the large black and white line running across the Roman town and generated by the magnetic signal of the gas main that is currently being worked upon. Sadly for us, the old main is not being lifted, as the magnetic signal was powerful enough to mask readings immediately around it and its removal would allow for more data on the Roman town to be recorded.

This work continues to add to our knowledge of Roman Verulamium. Much of its roads and city blocks of insulae have long been known from aerial photographs, while excavations have provided details of the forum and basilica complex that lies under St Michael’s Church and vicarage, and the second century theatre (a reconstruction image of which features on the front of this newsletter). Of the major public buildings only the bath complex remains largely unknown, although its location is clear and limited excavations took place on the site in the 1980s. While recent opportunities to excavate have been limited, work on projects such as this allows us to continue to recover information about the town.

David Thorold

Curator, Prehistory to Medieval, Verulamium Museum