Essayist: Some researchers criticize British governmental security agencies for not releasing enough information about sightings of unidentified flying objects (UFOs) made by these military and intelligence agencies.
Conclusion (this leads to)
It seems like there have been spacecraft sighted near Earth that are extraterrestrial in origin.
Evidence
When the British government gets requests from civilian researchers for information about sightings of UFOs made by military and intelligence agencies, those requests are brushed aside.
Evaluate
This author seems to interpret the brushed-aside requests for information as evidence that the British government has something to hide.
Isn't it possible that we could Explain this Curious Fact with some alternate explanation?
Maybe there really is nothing interesting to share with civilians and the British government is just annoyed by the frequent requests. Maybe there is something to hide, but it isn't "we discovered aliens".
Goal
Since this author is interpreting the meaning behind a Curious Fact, we can strengthen the argument by finding an answer that either - rule out an alternate explanation for why requests for info are brushed aside - boost the plausibility of the author's explanation, which is that the British government has sighted extraterrestrial spacecraft near Earth and is just unwilling to share info with the public about it.