The Berwyn Mountain Incident (The Welsh Roswell)

The Berwyn range rises above the villages of Llandrillo and Llandderfel, in what was then Merionethshire and is now Denbighshire. Its peaks include Cadair Berwyn at 832 metres, Moel Sych and Cadair Bronwen. At 20:38 on Wednesday, 23 January 1974, the Institute of Geological Sciences recorded a magnitude 3.5 earthquake in the Bala area. It was felt across North Wales and as far away as Formby.

No one knew yet that it was an earthquake. Residents heard a huge bang and saw a brilliant light in the sky. The shaking lasted about five seconds. Huw Lloyd was 14 and watching television with his sisters. "There was, like, a thud," he recalled. "The whole place started shaking quite violently, like an earth tremor."

Sergeant Elfed Roberts of North Wales Police was driving to Llandrillo with a senior officer. "All of a sudden we saw this green light in the sky ahead of us and it seemed to be an arcing light," he said. Calls poured into Gwynedd Police. One entry in the log read: "Circular light in the sky at estimated height of 1,500 feet. Object exploded and pieces fell."

Pat Evans, a district nurse from Llandderfel, heard the concussion from her kitchen. She thought a plane had come down. At about 8:45 p.m. she set off toward the Berwyns with her daughters Diane and Tina, who were both trained in first aid. On the slope of Cadair Berwyn she saw a red glow, with smaller flickering lights lower down.

Her statement was simple. "Bright red light, like coal fire red. Large perfect circle. Like a big bonfire." The light changed to yellowish white and back again. "There were no flames shooting or anything like that. It was very uniform, round in shape." When she opened the car window, she heard nothing. Small white lights zigzagged below it like Christmas tree fairy lights. She took them for rescuers. She was still watching at about 10 p.m. From a farmhouse nearby, Mike Saville watched the object from about 9:10 p.m. until it sank below the horizon ten minutes later.

About 10 police officers reached the area within the hour, followed by mountain rescue teams. RAF Valley searched as well. They found no crater and no wreckage. Rumours followed of soldiers, convoys and men in black. In the 1990s researcher Tony Dodd published an anonymous soldier's claim that two large, oblong boxes had been driven from Llandderfel to Porton Down. Dodd admitted that parts of it were hearsay, and the soldier's dates fell before 23 January. Porton Down stated that "no aliens, either alive or dead have ever been taken to Porton Down."

In May 1974 Brynmor John, the junior RAF minister, wrote that "the phenomena could well have been caused by a meteor descending through the atmosphere burning up and finally disintegrating before it reached the ground." A fireball had been seen that night from Cornwall to Northern Ireland. The seismologist R. M. W. Musson and others concluded that two unrelated events had happened within minutes of each other. In UFO Down, Andy Roberts and David Clarke argued that the nurse had seen poachers' lamps, and that the zigzagging lights were police torches.

The gamekeeper Scott Felton and the ufologist Margaret Fry disagreed. They placed the poachers on Cadair Bronwen, not Cadair Berwyn, and said they had gone by about 9 p.m. They also pointed out that lamping moves, while the glow on the mountain stayed still for about 90 minutes.

Pat Evans never changed her mind. "It couldn't have got there any other way apart from being flown there, so it had to be a UFO of some sort," she said in 2010. That was the same year the MOD files were released, and they framed the night as an earthquake and a meteor. The tabloids called it the Roswelsh Incident. Half a century on, one question remains unanswered: what was glowing on that mountainside?