Researchers looked for more treasure and, having located the crack where the hoard was hidden, eventually found 209 coins, forged in places as far afield as Constantinople and London and seemingly hidden in the late fifth century, a time when Roman civilisation in Asturias was losing ground in wars against Germanic invaders.

“This was a significant moment of expansion by the Suebi people in northwestern Iberia, with the area around Grado being a frontier territory”, archaeologist Alfonso Fanjul told El País newspaper.

The researchers believe the pieces found are only “a secondary deposit”, adding that there may be more coins in the cave, possibly deeper in the ground due to the burrowing activity of animals such as badgers.

The 209 coins were made of copper, bronze and, in the case of the largest of the haul, a 10-gram follis minted in Roman London – four per cent silver.

It is not the first time archaeologists have found treasure in the thickly wooded hillsides of Grado, with 14 gold coins from the reign of Emperor Constantine I having been uncovered nearby in the 1930s.

“The accumulation of significant finds could – with caution – be seen as a response to the intense conflict experienced in this border territory,” said Dr Fanjul.