Roman fort in Wales may prove Mabinogion tale of Emperor Magnus Maximus, Oxford archaeologist says

Merrony found the site in 2024 about 2 miles (3.5km) south-west of the summit of Frenni Fawr, the 395-metre easternmost peak of the Preseli Hills. Satellite imagery had shown a convincing outline in an overgrown field, and shortly after visiting he noticed a Roman tile that turned out to be the first of many. With financial support from Oxford University and crowdfunding, the excavation has confirmed his theory of the site and its significance, he said.

In The Dream of Macsen Wledig, medieval storytellers used the Welsh name for Magnus Maximus and described how he pitched his camp at Frenni Fawr during military manoeuvres. Until now there had been no archaeological evidence for a Roman marching camp or fort on the summit or below it. Merrony said he was excited that the landscape held the only Roman military site close to where the Mabinogion places the emperor. “If Magnus Maximus was there, there must have been an army there,” he said. “It’s such a remote area but the tale mentions the easternmost peak of the Preseli Hills, which is where this site is. The presence of a heavily fortified Roman auxiliary fort may help unlock the mystery of a Mabinogion legend that has endured for nearly 1,700 years.”

Before the dig, Merrony’s brother, Nick, had jokingly asked him to find a couple of coins to prove the Magnus Maximus theory. He later returned and asked, “well, are these any good?” Merrony said, “you’ve got to be kidding me.” Nick had found two coins dating from the late 4th century. Merrony said it was fascinating to consider that the two coins may be linked to the tale of Macsen Wledig—Magnus Maximus—in the Mabinogion, the Welsh equivalent of the Odyssey.

Measuring 180 by 150 metres, the fort is on a slope with a commanding view of the surrounding landscape. It is likely to have held about 500 troops. It has “a characteristic playing-card form, with rounded corners” and a perpendicular road, Merrony said. Finds so far include an unusual iron stylus, many pottery shards, large quantities of Roman tiles, extensive compacted clay floors, a common feature on Roman military sites, and even rut marks left by wagons.

A geophysical survey confirmed the presence of a rectangular building in the middle of the enclosure and a larger rectangular building immediately to the south. Merrony said this arrangement is consistent with the placement of a headquarters building orientated east and thereby “facing the enemy,” and a commander’s house. The discovery overturns assumptions that the area’s Indigenous Celtic tribe was on peaceful terms with the Roman invaders.

Merrony is a leading specialist in the Romano-British period. His previous discoveries include two Roman villas, at Ford in Pembrokeshire and at Cutteslowe in Oxfordshire. He identified a Roman road along the southern shoulder of the Preselis in 2022, challenging assumptions that the Romans did not venture far into Wales. His research will appear in Antiqvvs, a quarterly magazine dedicated to archaeology, ancient art and history. Magnus Maximus will also feature in Merrony’s forthcoming book, titled Lives of the Roman Emperors: From Augustus to Romulus Augustulus.