It started with a mission to remove a wooden pole to lay some cabling, but ended up revealing a centuries old mystery.
A secret tunnel that could date back to the 12th century, and not marked on any maps since at least the 1700s was discovered by workmen in Tintern, Monmouthshire.
They had been called to the historic village to move overhead power lines to a different part of a customer’s property.
But when they started digging a footpath along a fast-flowing stream, then found a four foot high passageway.
Technician Allyn Gore said: ‘Before work began we’d done all the usual checks and nothing had shown up on any of our drawings or records to indicate there was anything unusual about the site.
‘But shortly after the excavation began, the digging team made the extraordinary discovery of what they initially thought to be a cave.
‘Work stopped immediately and we were called in to decide what course of action we should take next.
‘I have previously been involved in other excavations where we’ve discovered old wells and cellars not shown on any plans, but nothing as exciting and impressive as this.’
Cadw, the Welsh Government’s historic and cultural heritage service, were then contacted and they sent someone along to check it out.
Allyn added that, although blown away by the find, both Western Power Distribution and Cadw made the decision to reseal the entrance to the tunnel to prevent the risk of damaging it before any in-depth archaeological examination could take place.
‘We backfilled the trench and reinstated everything because it could take years before any investigations are concluded.’
Tintern is situated in the heart of the Wye Valley Area of Outstanding Natural Beauty and the remains of its Abbey date back to the early 12th century.
Nearby are also an abundance of ruins from old furnaces, iron works and forges, and it’s thought that the tunnel – which was unearthed and then covered back over last October – might be linked to those.
Untraceable on ordnance survey maps dating back as far as the 1700s, no one living in the area, or anyone from the local authority, have admitted knowing it was even there.