One of the protocols for NOT releasing information is if the release of that information 'would cause embarrassment to a friendly nation'. If MoD are holding anything back, then that is almost certainly the reason why.
It is also worthwhile considering the implications of the wider political / defence situation at that time:
- The Cold War was in full swing
Soviets threatening to invade Poland but being warned off by the US President
NATO on increased alert as a consequence of that threat
Iran holding US hostages in Tehran
There had been a failed rescue attempt to free the hostages early in the year and a second attempt was planned. The second attempt was to use modified C130 aircraft fitted with jet engines. This second attempt was, allegedly, aborted
PM Thatcher took office in 1979
President Reagan elected to office in Nov 80
Iraq invades Iran in Sept 80
US supports Iraq
US has, allegedly being supplying BZ and mustard gas to Saddam Hussein since circa 1977
A recent British TV documentary investigating night flights of USAF aircraft from RAF Lakenheath suggested these aircraft could be flying false flag ops under Israeli colours - if true, then was something similar happening in Dec 80?
In July 80, Rt Hon Francis Pym, the then Defence Secretary grants the US permission to site Cruise missiles in the UK
Anti-nuclear protests in London and at RAF Bentwaters as a result
Allegedly, there was a major drugs bust at the twin bases just before Christmas. It is rumoured that some LE/SP personnel were involved. Several personnel were sent back to the States and other personnel, some apparently just out of training, were drafted in as replacements
HMG chooses its words very carefully. When HMG stated 'it was of no defence significance' then it was because they knew what it was. If they did not know, then they would not have used those words because if HMG had been wrong they would have been called upon to explain that statement and no government. least of all that of Margaret Thatcher, would have risked placing itself in that situation..
Further to all of that, much of what was highly classified in 1980 is now in the public domain so what could possibly link Dec 80 to today and why does whatever that might be have to remain secret?
Answer that and you've solved the mystery of the RFI