A SECRET medieval tunnel has been discovered in the Wye Valley.

The tunnel was discovered in Tintern, while Western Power Distribution (WPD) contractors were excavating a trench there.

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.

South Wales Argus: Secret tunnel unearthed beneath Tintern Pictures: Western Power Distribution

Secret tunnel unearthed beneath Tintern. Picture: Western Power Distribution

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.

“Shortly after the excavation work began, the digging team made the extraordinary discovery of what they initially thought to be a cave.

"I have been involved in other excavations where we have discovered old wells and cellars not shown on any plans, but nothing as exciting and impressive as this."

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

South Wales Argus: Secret tunnel unearthed beneath Tintern Pictures: Western Power Distribution

Secret tunnel unearthed beneath Tintern. Picture: Western Power Distribution

The tunnel system was tucked away underneath a footpath, running parallel to the Angiddy Brook, and seemed to follow the brook’s route along the valley.

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."

South Wales Argus: Secret tunnel unearthed beneath Tintern Pictures: Western Power Distribution

Secret tunnel unearthed beneath Tintern. Picture: Western Power Distribution

The ruins of Tintern Abbey date back to the 1100s and are just a short distance away.

The tunnel is not shown on any Ordnance Survey maps dating back as far as the 1700s.

After consultations with Cadw, it was decided to stop all work and seek an alternative route to prevent the risk of damaging or reducing the integrity of the tunnel, while further investigations take place by archaeologists.

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