Night-time treasure thieves threatening a nation's heritage

Police found more than 50 holes had been dug among the graves overnight

As darkness falls in one corner of Wales, police officers begin their hunt for treasure thieves - a crime that would sound like fantasy if it wasn't for the evidence.

In Gwent Police's patch, the hills are littered with ancient forts and Roman remains - and have become a regular target for those hoping to unearth rare artefacts for the black market.

Often, investigators are left with nothing but a hole in the ground - with little idea of what has been stolen or its value - though some looted treasures have been worth millions.

Nighthawking, as it is nicknamed, is now seen as a genuine threat to the nation's heritage.

PC Dan Counsell had never heard of the term nighthawking before he took a call in September 2019.

He was told locals of an ancient village near Chepstow had awoken to find more than 50 holes mysteriously dug among the gravestones of their churchyard.

Residents were horrified and newspaper headlines spoke of "grave robbers."

PC Counsell understood the upset - many of his own family members, including grandparents, were buried there.

In truth the robbers weren't interested in the dead, but the artefacts that may be buried beyond them, deep into the Earth.

Before it became a Christian church about 700 years ago, there were Romans here.

Ancient standing stones hidden in the woods of south Wales' hill forts have become targets for treasure thieves

Among the holes, some dug on top of the graves themselves, were discarded bits of old metal - a telltale sign that those practising in the "darker underbelly" of metal detecting had been here.

Known in the archaeological community as nighthawkers, they use the cover of darkness to access sites they have no legal right to disturb in the hope of unearthing treasure.

Some do it for the thrill of building their own private collection, others are thought to smuggle items abroad in the hopes of selling them to the highest bidder.

It's not uncommon for illicit finds to appear on online auction sites.

Archaeologists and police point out this is a small number of people in an otherwise hugely respectful community of metal detectorists.

These coins were from a stolen Viking hoard worth £3m - most of which has never been recovered

In one of the most recent high-profile cases, two men from south Wales were found guilty of stealing a hoard of Viking gold from Herefordshire worth £3m - most of it has never been recovered.

After PC Counsell's first case in the graveyard, he began looking out for the phenomenon.

Within two years his team had uncovered 23 suspected incidents in the force's patch - a 600 sq mile (1,550 sq km) corner of south-east Wales peppered with imposing castles, ancient hill forts and Roman ruins.

Police have been getting reports of people digging in fields at night

Reports of people in fields at night and mysterious holes being discovered has all led PC Counsell's team to uncover cases of nighthawking.

He said one of the most worrying things was that most targeted Scheduled Monuments - a term used in the UK to describe archaeological areas of great national importance.

Cadw, the authority charged with protecting Wales' 4,000-plus protected ancient sites, said it saw 10 to 20 nighthawking incidents each year, but that the nature of it meant was very likely underreported.

It often relies on an eagle-eyed member of the public spotting an unusual hole in the ground and deciding to report it to police, rather than discounting it as the work of a badger or rabbit.

Police say nighthawking holes are distinctive and often feature clean cuts on three sides - sometimes with discarded metal laid out nearby.

Dr Jonathan Berry, Cadw's senior inspector of ancient monuments and archaeology, said sometimes there were innocent explanations, like hobbyists not understanding the rules.

Others, however, were motivated by "greed", with elements of organised crime.

"In terms of where these things go, that's kind of murky, but very often finds are sold on things like online auction houses, antiques centres, things like that," he said.

"It could also just be private networks, social media. You can find items of significant rarity and value can be out of the country and in other collections very quickly."

The fields near the churchyard targeted by "grave robbers" have become a hotspot for activity

According to police, often the sites targeted are remote, treacherous even, and reminiscent of an Indiana Jones expedition - minus the booby traps.

One site PC Counsell takes us to, a series of standing stones, is through dense woodland, up a steep mountain track - even in a 4x4 with a trained police driver it's a hairy climb.

To think treasure hunters could be making the journey in the pitch-black sounds fanciful and yet this site has fallen victim to nighthawking multiple times.

"Clearly their remoteness is attractive to potential criminals. They see these sites as being safe in terms of not being disturbed or apprehended."

In an attempt to even the odds, the rural crime team has been using thermal imaging cameras attached to drones and binoculars capable of picking out suspected treasure thieves on a pitch-black mountain side.

Recently, that helped them catch a suspected nighthawker hiding behind a pile of manure after his footprints on the fresh dung heap shone up on thermal imaging.

"It's a really hard crime to detect," said PC Counsell.

"Yet on at least six to eight occasions we've discovered people illegally metal detecting."

Police have been using thermal imaging to spot any potential treasure thieves returning to the graveyard targeted in 2019

None of those caught so far have been the ones accessing Wales' legally protected ancient sites, but Gwent Police hopes the frequent night patrols and new technology will get results.

"The sadness around it all is that these are scheduled ancient monuments for a reason - because they are recognised as being of national historical importance," said PC Counsell.

"If something is removed that we are unaware of, it could be really important, we just don't know.

"Once that item is gone it's gone forever. It's having a big impact on the nation's heritage."

A 17th Century silver thimble found in Flintshire was recently declared as treasure after being handed in by a metal detectorist

When somebody finds something that could be treasure, they have a legal obligation to declare it.

They are not allowed to keep it, but if they followed the rules and unearthed it from land they had permission to be on - then they will be paid a share of its value once it's bought by a museum.

This sees experts such as Sian Iles, a curator at the National Museum of Wales, brought in to give their verdict on whether any potential item meets the threshold for treasure.

There are several steps, but loosely speaking an item should be "old and gold".

In Wales the general threshold is more than 300 years old and made up of at least 10% precious metal.

"Every treasure find helps us to build a picture about the decisions people in Wales were making in that time period, about their fashions or their beliefs," said Ms Iles.

Sian Iles helps to assess whether an item should be considered as treasure

The senior curator of Medieval and later archaeology said the number of finds being declared to the National Museum had been going up year-on-year since 2019.

Ms Iles and her colleagues assess about 70 potential pieces of treasure each year and believe the vast majority of metal detectorists are doing the right thing and wanted their finds to be used to help historians.

She recently helped assess a silver thimble found in a field in Flintshire by metal detectorists which was then declared treasure.

She added: "Even the smallest object can really bring in important information about people in the past."