VIDEO footage offers a glimpse into a tunnel beneath Tintern which was unearthed by contractors.

A Western Power Distribution crew made the surprise discovery while excavating a trench.

When contractors began excavation work, after a customer requested the relocation of a pole on their property, they unearthed an ancient and unknown medieval tunnel.

WPD Technician Allyn Gore, who headed up the team, said: “Nothing had shown up on any of our drawings or records to indicate there was anything unusual about the site."

Further investigation revealed it was a man-made tunnel, around 4ft in height.

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It may have been unknowingly walked on for centuries.

Cadw sent a representative along to the site.

"He was very impressed with the sheer scale of the tunnel and quite fascinated to see it," said Mr Gore.

"In his opinion, it could possibly be linked to the iron work ruins previously discovered in the area."

The tunnel has now been filled back in in order to prevent damage to potential archaeology.