The 1977 Broad Haven Triangle sightings are being remembered with a special 40th anniversary event.
An explosive novel revealed details of a declassified MoD document which suggests top-ranking officials carried out a covert inquiry into the 1977 sightings in Wales.
The area was gripped by UFO and paranormal fever after several people saw lights and objects hovering in the sky, a being in a metallic space suit, while poltergeists allegedly plagued one family, animals were seen cowering and ghostly figures reportedly peered into farmhouse windows.
Among the witnesses were 14 children who all drew similar pictures of a craft said to have landed near their school.
The book – The Watchers by Neil Spring – is said to be based on “true events” and claims to reveal the truth about what really happened at remote Broad Haven along a strip of rugged coastline in Pembrokeshire National Park near an RAF base.
Mr Spring, who is a key speaker at the event on Saturday, researched the case through documents sent to the National Archives 30 years after the bizarre happenings and after a new witness came forward.
At the time, MoD officials expressed no interest in the sightings, saying there was no threat to national security.
However, among the documents was a letter from the head of the MoD’s S4 wing to the Provost & Security Service, the RAF’s internal police force.
The S4 chief wrote “I have not even told the Minister I am consulting you” and called for a “discreet enquiry” after expressing bewilderment at the number of apparently “level-headed” witnesses to the strange activity.
Mr Spring said: “(The new witness’) testimony rocked the very foundations of the British Government.
“I visited Broad Haven a sceptic, and came away convinced that some of the locals knew far more about the mysterious occurrences of 1977 than they are willing to reveal.”
The disclosures prompted Tory peer Lord Black of Brentwood to call for a full explanation from the MoD of what it uncovered.
The Tory peer has been long involved in getting official government files of UFO sightings and inquiries made public.
Lord Black said: “A number of recently released MoD files leave little doubt that a small number of sightings of aerial phenomena – particularly by military personnel, pilots and air traffic controllers – remain unexplained and unidentified.
“There needs to be further examination of these issues in the hope of learning something new.”
Three years ago a former US Navy sailor came forward to say that the cause of the silver-suited being was in fact a US military personal wearing their standard fireproof uniform and the UFOs were new harrier gets being flown.
Since disbanding a unit set up to investigate alleged UFO sightings in 2009, the MoD will no longer comment on the subject.
The Swansea UFO Network is holding a Welsh Triangle 40th Anniversary Conference in Broad Haven from 10am to 5pm.
Dubbed the “West Wales flap” of 1977, the incident was second only to the “Warminster Thing” in British UFO history.