The discovery of a few muddy coins in a Devon paddock by a pair of amateur metal detector enthusiasts has led to the redrawing of the boundary of the Roman empire in south-west Britain.

Previously it had been thought that Ancient Rome’s influence did not stretch beyond Exeter but the find has resulted in a major archaeological dig that has unearthed more coins, a stretch of Roman road and the remnants of vessels from France and the Mediterranean once full of wine, olive oil and garum – fish sauce.

The far south-west of Britain has long been seen as an area that clung to its independence but the discovery at Ipplepen, near Newton Abbot, 20 miles south-west of Exeter, has led to the conclusion that Roman influence was strongly felt here.

It is also fair to surmise that the Roman road probably did not stop at Ipplepen but would almost certainly have carried on towards the modern town of Totnes and possibly even further south and west.

Danielle Wootton, the Devon finds liaison officer, said she was intrigued when the metal detectorists Jim Wills and Dennis Hewings told her about the Roman coins they had found in the Ipplepen paddocks.

“Then more and more coins were found, which is really unusual in this area,” she said. By the time 150 coins had been uncovered it was clear that Wills and Hewings had happened upon something important.”

A geophysical survey was commissioned, which revealed the presence of ring ditches, which are associated with iron age roundhouses – and the Roman road. The project is a collaboration between the University of Exeter; the Portable Antiquities Scheme, which is run from the British Museum; Devon county council; and Cotswold Archaeology. Experts, students and local volunteers began the painstaking process of digging and sifting to try to establish exactly what was here.

Work at the site in Ipplepen. Photograph: University of Exeter

The conclusion is that the road was probably built by the Roman army in the 50s AD and improved and restored over the next 300 years. Probably as interesting as the road are the pieces of pottery that continue to be unearthed almost every day.

There are ordinary, coarse sherds that would have come from everyday cooking pots and bowls. But there are also pieces of “samian ware” – fine kitchen bowls originating in France. One of the fragments appears to show a human figure, possibly Hercules, wielding a club. Handles of amphorae, which would have carried wine, oil and sauce, have also been found.

It may be that this was a Romano-British settlement where native Britons traded with the Romans – hence the coins – and got a taste for elements of their lifestyle.

Wootton said: “The presence of these kinds of vessels demonstrates that the people living here were at least influenced in some way by the Romans – they have adopted Romanised ways of eating and drinking which shows that some of the locals developed a taste for Mediterranean products such as wine and olives.

“However, the settlement is still puzzling as it does not really compare to other known Romano-British settlements in neighbouring counties to the east such as Somerset, Dorset and Wiltshire. Sites from those counties produce more finds such as coins and brooches and a greater amount of pottery.

“We are wondering whether the Dumnonii, the tribe who lived in the area now known as Devon, still retained their traditional identity rather than becoming entirely Romanised.”

Another find at the site is a cemetery next to the Roman road dating from the 6th to the 8th century, suggesting that people lived on the spot for around 1,000 years before – for reasons unknown – deserting it.

Sam Moorhead, an expert on iron age and Roman coins at the British Museum, said the work that is continuing at Ipplepen was important. “This has lifted the lid off a whole series of new questions which need to be asked about Roman Devon,” he added.