Pentyrch and Smilog Wood

EPISODES: INTRODUCTION | The Egryn Lights | The Welsh Roswell | The Pembrokeshire Wave | Pentyrch and Smilog Wood

Episode 4 of UFOs, Aliens and the Fairy Kingdom by Nigel Graddon.

Pentyrch and Smilog Woods

I met Caz Clarke in Pentyrch in September 2022, together with my friend and neighbour Deiniol Morris, acclaimed musician, artist and film-maker. At the time, “Deins” and I were working on a potential three-part film project, one part of which related to the Welsh UFO scene.

We met Caz at the five-bar gate at the end of Heol Penllwyn, beyond which are the fields where witnesses described remarkable scenes that took place more than six years earlier. Caz and her neighbours have come in for considerable criticism about their UFO experience that night in February 2016, with many expressing doubts that they had actually seen what they described.

Deins and I found Caz to be genuinely steadfast in her belief that she had been privileged to observe a series of profoundly moving anomalous “alien” activities, and we saw no reason to doubt the veracity of her description of events. Clarke reportedly passed multiple polygraph examinations (“truthful with no deception indicated”) to support the reliability of her testimony.

Military planes and helicopters, a chase, explosions, physical effects such as shaken buildings, damaged trees and wreckage on the ground, an Apache helicopter landing with its cockpit on fire, weird snow and mystery men in white coveralls—these sound like components from an X-Files storyline. Nevertheless, all this really happened on a cold winter’s night in south Wales in 2016.

From Welsh publications and open sources, including Wales Online, The Cardiffian and blogs, we learn that eyewitnesses in Pentyrch, a village on the western outskirts of Cardiff, reported observing on the night of Friday, 26 February 2016, a massive pyramid-shaped light descending toward the ground.

In nearby Llantrisant, starting around 2 a.m., residents were disturbed by a great commotion—the sounds of military helicopters above the town. People took to social media. One person complained to police, ‘What’s going on in Llantrisant? Something definitely woke me and now there’s a shitload of helicopters circling outside.’ The helicopters were seen to land on the local common. The landings and commotion lasted for many hours. One distressed resident complained about the presence of a big double-engine Chinook military helicopter. She said it just missed her chimney. Others said that they were causing houses to shake. People asked if their children and livestock were in danger.

The official line was that the activity was related with Exercise Chameleon, a bi-annual training drill between the British army and the RAF. As this was a completely normal exercise, the Forces said it was not necessary for local people to worry. The exercise periodically includes low-altitude helicopter and C‑130 operations, parachute drops, and flare simulations. However, all this was official dissemblance. Exercise Chameleon was a joint operation in Durham, which ran the week before the 26th and is 300 miles from Llantrisant.

Pentyrch lies on the southern slope of Garth Mountain, known as “The Garth.” The summit is just above the village to the north and is surmounted by a bronze-age burial mound, on top of which is a trig-point at 1,007 feet (307m). The mountain is easily recognisable for miles around due to the “pimple’ on the top. Several ley lines intersect near the village and there have been many UFO sightings here over the years.

On that extraordinary night in Pentyrch, Caz Clarke and neighbour “Dave” walked to the eastern corner of a nearby field. Her neighbour ventured onto the pasture.

It had started a few days earlier, the 23rd, when Dave saw a small grey twin-propeller plane flying slow and very low in a figure of eight pattern over the village. Then it switched to flying in a large circle before resuming its 8-pattern. This went on for three days and three nights continually. At no time in this period did observers leave the airspace unwatched. One plane would arrive before the other would leave and not a minute before.

On Wednesday, the 24th, they saw a second plane, which swapped places with the first. The two plans were a Hawker Beechcraft 300 and a Britten-Norman BN-2T Turbo. The air space over the village was evidently under constant observation. It was established that the whole of Welsh airspace was closed to all traffic on the night and early hours of 25th-26th February.

On the evening of Thursday, the 25th, an E3 Sentry, an early warning and control aircraft with a rotating dome on its fuselage, circled the sky over the fields. When it banked, the moonlight illuminated a mushroom on its back. It circled seven times. Then, at around 2.40 a.m., a red light became visible above and beyond the trees that marked the field’s western edge. It was followed by other red lights that formed the outer edges of a huge pyramid. The pyramid tilted to the right, turned very slowly anti-clockwise and started to move away. Soon, the red light became three, and the apex of a pyramid entered the space on an oblique angle. It was not seen to “arrive,” but rather emerge gradually as if through a tear in space.

Another witness, resident Mike Henbury who was taking his dog for a walk along Tyn-y-Coed Road just after midnight, said the red pulsing light was very large indeed. It didn’t touch down totally but reached 10 to 12 feet from the ground when it lit up, showing its full outline, then it dimmed down.

Resident Peter Piper said, ‘I tried to identify the helicopters around 3:30 a.m. to 4.10 a.m. but due to their altitude and cloud base this proved difficult. I didn’t hear any Chinooks, but what I did see sounded and looked approximately the size of US Sikorsky Black Hawk Helos.’

When the triangle of lights lined up behind trees by the field, it ejected a bright green starlike object as if fired from a cannon. Meanwhile, the large craft was descending lower in the sky towards the ground. It appeared to be landing. The E3 Sentry began flying up and coming back round again.

Bright red lights towards the bottom of the craft changed to sodium orange, and fingers of arcing light raced to the ground. The red lights then flicked off and the large object became invisible.

Dave saw a large number of red and green orbs dance and gather into one. One of red orbs slowly rose, stopped and turned to green, flashed very fast, and slowly moved off. Two aircraft followed it. The planes in the sky, the E3 and two more U.S. planes that had since arrived, were joined by a C-130 Hercules aircraft.

The green object then moved west in the direction of Llantrisant. Many residents there reported low-flying helicopters, building-shaking explosions, and lights intrusive enough to shine into homes around 2–4 a.m.

A nurse at Royal Glamorgan Hospital reported hearing loud explosions just after 2 a.m. and a second blast, smelling sulphur, and seeing smoke entering through vents and windows. She doubted the military drill cover story, noting the closure of local roads and matching local social media claims.

Other local residents, including Diane Blackmore and Christopher Buckley, recalled prolonged low-flying helicopters, red pulsing lights, and ground disturbances consistent with parachute flares or hazard-marking operations. Residents in the neighbouring Talbot Green area reported seeing the green light being chased, and then being shot down by an aircraft.

Military planes flew back and forth from St Athan to Llantrisant for hours during the night, as if they were transporting something.

Herald.Wales reported that the event provides rich detail on eyewitness testimonies—describing multiple shapes, lights, explosive sounds, tree damage in Smilog Woods near Llantrisant, alleged suppression of media footage, and claims of intimidation and suspected clean-up activity by military personnel following the incident. It calls the Pentyrch case “the greatest UFO cover-up of the 21st century.” It underscores the rain-like lightning tendrils, red-to-green object timing, phone malfunctions, and MOD’s Section 26 refusal to release details.

Clarke and collaborator Gari Jones investigated Smilog Woods, finding a burnt path of snapped trees and vegetation apparently scorched or destroyed—possibly aligned with where one of the smaller craft may have crashed. They measured elevated electromagnetic field levels (EMF) safety thresholds in certain spots, especially where the pyramid was seen closer to the ground.

Investigators with the Swansea UFO Network (Emlyn Williams, Steve Drewson and Mike Maunder) also found the terrain in Smilog Woods visibly damaged—snapped 40-ft trees and scorched vegetation—and measured persistent EMF readings reaching 1.2 milli‑tesla (3× the normal safe threshold) even years later.

Reports reference mysterious foam or “angel hair,” or pseudo-snow observed at the site; some users suggest it comprised silica-rich particulate matter reported in other UFO incidents. Physical disruptions included heavy military vehicle tracks, reports of road closures with inconsistent explanations, and attempts at intimidation (an unknown vehicle trying to run Clarke off the road, on one occasion) during early investigation visits.

The Project Condign study (1997–2000) offers scientific context by exploring electromagnetic and plasma-based phenomena (like “buoyant plasma”) that can explain strange lights, EM effects and levitating visuals. Its findings offer natural explanations that could align with reported EM anomalies and sensory effects in Pentyrch. Though not directly connected to the Pentyrch phenomena, it provides a possible alternative naturalistic explanation for witness-reported anomalous fields and visual effects.

Wikipedia’s entry on UK UFO sightings includes this incident with a summary of an unusual pyramid-shaped light that descended and emitted two smaller objects before military aircraft arrived.

Clarke gave a detailed interview on UFO Chronicles Podcast (Episode 100), describing the pyramid, barrel craft, pursuit by military vehicles, and a crash site filmed the next morning. Military personnel allegedly camped at the site and offered misleading cover stories before relocating.

Coverage also appeared in blogs (including the Clayton Graham blog, which offers a summary of Clarke’s motivations, polygraph efforts, crowd-sourced reports of widespread witness calls/emergency calls, radar sightings, and damage assessments), local journalism, and UFO-focused websites, presenting Clarke’s narrative and broader community concern over official accounts.

Clarke filmed the crash site next morning, and shortly thereafter uniformed personnel appeared and offered fake cover stories. The Podcast also notes that an Apache helicopter performed an emergency landing at Cardiff—a detail matching seismological tremors recorded ~40 miles away.

The UnidentifiedPhenomena.com page summarizes various data, including seizure-like helicopter activity around 2 a.m., some distressed emergency call transcripts, eyewitness reports of Chinook and Apache helicopter presence, local explosions, and anomalous residue or foam. The narrative includes mentions of spotter aircraft preceding the event and tree-damage inspections. It also references direct seismograph readings and describes Clarke’s assertion that phones and cameras failed during the event.

Reddit community discussions provide insight into both supportive and sceptical viewpoints. Supporters often highlight the consistency of accounts and local physical disruption:

“Multiple eyewitnesses, over 100 to date, describe the same thing… Forest indent appeared same night… EMF levels … 6× normal”.

“The whole town was told [about] Exercise Chameleon. …

“Really great evidence of something huge and wedge shaped being shot down by UK military. 60’ trees snapped off and suddenly dead ‘burnt’ plants… Seismic record of the crash…”.

“All cell phones in area not only lost connection, they became inoperable… That’s what over dozen witnesses have said!”

“I lived a few miles from Pentyrch… I remember hearing a lot of military planes flying about… it was called Exercise Chameleon

Credible alternative explanations suggest that flares (C‑130 Angel Wings), drop zone markers, night parachute operations, and military helicopters could account for much of what was seen. In experienced military circles, large flares can form pyramidal light patterns in the sky, which may be misinterpreted by untrained observers. The fact that phones reportedly failed to record footage fuelled speculation of electromagnetic interference or equipment shutting down—though sceptics point out that poor reception and darkness often prevent clear capture in rural areas.

Sceptical remarks included:

“My opinion … is that she saw a military exercise involving the RAF, British Army, SAS… called Exercise Chameleon. … flares can easily form a triangle shape at night…”

“She didn’t know a military exercise was underway … jumps to a primed conclusion that it was space aliens.”

Another sceptic noted that Clarke had prior interest in ufology and may have misinterpreted flares, training markers, and parachute operations as extraterrestrial craft.

Multiple Freedom of Interest (FoI) files regarding the Pentyrch incident have been released by the Welsh Government:

• FOI release 17096 – “Pentyrch incident” (59 KB PDF), published 28 February 2023

• FOI release 16842 – same subject, published 30 November 2022 (58 KB)

• FOI release 19542 – “Details of alleged UFO incident at Pentyrch,” published 13 May 2024 (86 KB)

Each file contains the formal Welsh Government response to public requests. The documents reportedly state that no records exist showing permissions granted to close woods, paths, roads, or to use explosives, raising questions if military action occurred without legal authority.

The case remains active in UFO discussion circles, with supplemental podcasts, books, and online forums keeping the story alive.

Caz Clarke has told me that, in her opinion, the Pentyrch event is one of ‘the biggest cases in the UK and possibly the world.’

Together with independent UFO researcher, Gari Jones, Caz Clarke has published her own account of the event.[1]

The next chapter considers the vexed question: Just who are our otherworldly visitors? Do they hail from planets in deep space, or may their homeland be much closer to ours than one may imagine?

In the fourth of the Indiana Jones series, Indiana Jones and the Crystal Skull, Indy asks John Hurt’s character, Harold Oxley, about the alien visitors’ startling mode of departure.

‘Where did they go? Space?’ he asks.

Oxley who had it figured all along replies, ‘Not into space, into the space between spaces,’ which in the movie’s storyline is the origin point for interdimensional beings that visited the Earth in their flying saucer and, subsequently, became the gods of the South American Ugha tribe. In his book Forbidden Science Jacques Vallée wrote:

The UFO phenomenon exists. It has been with us throughout history. It is physical in nature and it remains unexplained in terms of contemporary science. It represents a level of consciousness that we have not yet recognised and which is able to manipulate dimensions beyond time and space, as we understand them. It affects our own consciousness in ways that we do not fully grasp and it generally behaves as a control system.

Vallée believes that when we perceive an inexplicable event, whether it be a UFO and its occupants or a glimpse of the “wee folk,” what we experience is a sequence of actions arising from a spiritual system that acts on humans and uses humans as the medium by which to communicate beyond our ability to understand. Vallée is not alone among researchers and scientists in his belief. Quantum physicists, for example, are expressing their belief in the concept of the multiverse, dimensions of existence that interlace all parts of our universe, our Earth a component part of this vast matrix of “space between spaces.”

It is increasingly speculated by Vallée and his contemporaries that the visitors in our skies are members of a recondite body of intelligent energy forms, such as the fairy folk, nature spirits and crop circle makers, which inhabits our planet’s companion planes.

Legend and myth tell us that these forces, as much a part of the Earth’s total corpus of life, both visible and invisible, as ourselves have always been here. It is this proximity that makes it a virtual certainty that from time to time we will feel, see or even meet our unusual neighbours on the other side of the fence.

The vital factor in this process is that the episodes of seeing and meeting are usually instigated by our exotic neighbours, who have us at a disadvantage because they have a key to our back yard, whereas we have no means of accessing theirs except either through our dreams and imaginings or by being taken there…willingly or not.

In the first chapter of Part 2, Non-Human Entities, we investigate the nature and forms of “alien” visitors—“UFOlk”—that witnesses, predominantly since the Roswell events of 1947, have variously reported either seeing, meeting, or, in some instances, being brought by them into craft, sometimes pleasurably, others in terrifying circumstances.

[1] Clarke, C. and Jones, G., The Pentyrch Incident: The Greatest UFO Cover-up of Modern Times, Independently Published, 2021.