A UFO researcher was so worried about the threat of UFOs he felt compelled to write to her Majesty herself, declassified files have revealed.
The letter, sent from Victoria, Australia in March 2009 was addressed: "Your Majesty Queen Elizabeth II.
It started: "I am writing to you to inform you Madam that the British Government continues to refuse to reveal the truth behind their files and reports of Unidentified Flying Objects (UFOs).
The writer went on to say there was more to UFOs than "weather balloons, airplanes, helicopters, lights, or natural phenomena" and said they had tried to contact various UK government departments, from the RAF, MoD and even MI5, to persuade them of the "seriousness of this UFO security issue".
The letter added: "These Unidentified Flying Objects (UFOs) are, I believe, a threat to the United Kingdom in view of the air and safety issues involved.
"As I am writing this letter to you Your Majesty, I contemplate whether or not you will see reason and if you will choose to act Madam?"
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The letter closed: "As a UFO researcher, I must highly recommend you act now Your Majesty.
"You are capable of deciding your own destiny.
"The question is Your Majesty, which path will you choose?
"I await your immediate action and response to this serious UFO issue.
"I have the honour to be, Madam, Your Majesty's humble and obedient servant."
A reply from Buckingham Palace, included in the files, said: "The Queen has asked the Private Secretary to thank (the unnamed recipient) for his letter of 18 March.
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"Although this is not a matter in which Her Majesty would intervene, the letter has been passed to the Secretary of State for Defence, so that this approach to the Queen may be known and consideration given to the points raised in the letter."
The writer was later sent a reply from the MoD, saying that although the government took the defence of UK airspace very seriously, there was no clear evidence that UFOs were a threat to national security.
A separate letter in the files was written to former prime minister Gordon Brown, urging him to take a more "active role" in the subject of UFOs.
The letter, written to Mr Brown in 2008, said: "Following the release of the UFO files by the Ministry of Defence, does the prime minister now feel it is time to take a more active role in this subject.
"I don't believe a prime ministerial position in Britain is enough to have knowledge of extra terrestrial life etc but feel that now public interest in this subject is at an all time high it would be a good time to show more governmental involvement, thus inspiring the electorate & winning the hearts & minds of the public.
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"This must be done in a professional manner & also handled subtly & seriously & most importantly with respect, so as to avoid becoming a laughing stock.
"The public do have an increasing fascination in this subject, regardless of whether they like to acknowledge it, & would love the government to take the first steps into a more intriguing future.
"Thank you for your time."
A slightly less sombre letter was a plea from a schoolchild asking for answers on whether "living things" exist outside Earth.
The letter, sent to the Ministry of Defence in January 2009, said the child and his or her father had seen "little air crafts" in the sky.
The MoD, which closed down its UFO desk later that year, replied to the writer, as well as sending "RAF goodies".
The letter reads: "To Mr/Mrs. Please tell me if living things live out side our planet.
"I would like to now because me and my father have seen little air crafted in the sky. And my father have seen 2 little light dancing around each other.
"Pleas send me a letter Telling me the answer."
The letter, received from a child in Altrincham, Greater Manchester, includes a picture of a flying saucer with an alien waving.
MoD staff replied in February that year, saying: "Thank you for your letter asking if there is life outside our planet.
"It's an interesting question and we remain totally open-minded about it, but we don't know of any evidence to prove life exists in outer space.
"We do look at reports of 'unidentified flying objects' but only to see if the country's airspace might have been affected but we haven't had any evidence of this so far.
"I am enclosing some RAF 'goodies' that I thought you might like."