IT is the evening of January 23, 1974. The sleepy farming community of Llandrillo is about to be woken with a jolt – one that will be talked about for many years to come.

It is an incident that returns to the fore today with the release by the Ministry of Defence of previously classified files.

Picture the scene: it’s about 10pm and pitch dark.

The streets of the village are lit only by the occasional streetlamp and the flickering light of TVs in people’s front rooms.

All is silent but something strange is about to occur.

Among a raft of classified “UFO” documents, presented to the National Archives by the MoD and made public today, is a file referring to what became known as the “Berwyn Mountains incident”.

Included is a letter, dated February 14, 1974, outlining five separate reports of “unusual objects seen in the sky”, in different areas of the UK, on the night of January 23.

According to the letter, these were all in the South of England and all described a bright light falling to earth. It suggests that these may have been a “bolide”, a meteor disintegrating during its passage through the atmosphere.

Another document is an extract from the meteorological logbook of the SS Tokyo Bay travelling from Port Kelang (Malaysia) towards Southampton.

The report describes “five bodies, spectacularly incandescent... traversing the sky”.

The ship’s captain, M. Lees, attributes the observation to a satellite disintegrating having re-entered the earth’s atmosphere and an attached MoD memorandum suggests this was “probably of the decay of the Soviet Communications relay satellite Moluiya 2-8’s rocket body which decayed at about this time”.

What has all this got to do with the mountains of South Denbighshire?

Another letter, a redacted correspondence from the MoD offices in Whitehall, provides a clue.

It reads: “With regard to the events of the evening of January 23 in the Berwyn Mountains; we did receive a number of reports of an unusual object seen in the sky just before 10pm on the evening in question...

“Later on, personnel of the Royal Air Force mountain rescue team participated in a search of the area where the object was thought to have come down, but as you probably know nothing was found.”

The theory is that, whatever was seen over other parts of the UK that night, eventually crashed into the Berwyn mountains, near Llandrillo.

According to an interview with a nurse who claimed to have witnessed the scene, she was confronted by “a huge pulsating orange ball at the top of the mountain with a few little lights almost like fairy lights flashing about it”.

One classified document, just released, would seem to suggest the nurse was not the only witness, stating: “People living in the vicinity of the Berwyn Mountains in North Wales are reported to have seen a brilliant ball of light apparently accompanied by a flash and an immense bang.”

But it is not just what might have been seen and heard, but also what would have been felt.

It has been deemed a coincidence but, at roughly the same time as the strange light appeared over the Berwyns, there was an earthquake measuring 3.5 on the Richter Scale, centred on the area.

Frustratingly, a large proportion of the material made available by the National Archives provides few clues about what really happened at the “Welsh Roswell”.

There are, however, a couple of documents in the files that do stand out.

These are a letter from a UFOlogist and the response to that letter from the MoD’s Directorate of Air Staff (Lower Airspace).

There is no denying that the UFOlogist’s theories seem far-fetched.

Among them he suggests that, on January 23, there was a military exercise taking place on the “Jerby (sic) Range on the Isle” and the coastguard had been told to expect activity on the North Wales coast.

He goes on to propose that “at the same time two squadrons of jet fighters were involved in an operation around Puffin Island and Capel Curig. Where a bogey did not return an IFF (identification friend or foe) signal subsequently the object was brought down at Llandrillo, where it and the five occupants where taken away.”

What is interesting, though, is the response to these suggestions.

The MoD respondent states: “First you mention ‘an exercise from Jerby Range on the Isle’. There was a RAF station called RAF Jurby Head which supervised an air weapons range off the north west coast of the Isle of Man and it is possible that military aircraft were using the range on January 23, 1974.

“However, the range closed in July 1993 and I am not able to confirm these details.”

In response to the UFOlogist’s second suggestion, the respondent states: “Again it is possible that there was a small squadron exercise being conducted in this area, at this time.

“However, if an air defence system had detected an aircraft that was considered to be a potential threat to the UK, it is unlikely that exercise aircraft would have been used to intercept it.

“It is also extremely unlikely that any aircraft would have been ‘brought down’ over land, however sparsely populated.

“When military aircraft are training they do, of course, simulate such scenarios and references such as those you describe may have been heard on their radio frequencies.

“Records of these small exercises are not retained for long periods and even if it were possible to identify which squadron these aircraft came from, it is doubtful whether any records would have survived.”

Interesting, but far from conclusive. So what was it? Meteorite? Soviet satellite? Military exercise? Alien spacecraft? Or men catching hares?

The Berwyn Mountains incident has always been a fascinating and frustrating mystery and despite the release of these latest documents, I’m afraid to say it remains so.

The files are available to download for free for a month at www.nationalarchives.gov.uk/ufos