It all started with a chance remark last year, a question I put to my father.

My old man was a pilot in the Royal Air Force for many years, in that interesting period of world history after the Second World War known as the Cold War. He had flown all over the world, in an age where this was very unusual. He had even dropped bombs on Suez during that ill-advised political embarrassment.

Dad is, or was, I should say, a great raconteur, a pillar of the local Rotary Club and very much in demand for his after-dinner speeches. He had a great fund of stories and anecdotes, often based on his flying experiences. But there was one tale which I had not ever heard him tell, one which I discovered buried in the draft of his autobiography when I was reading the proofs. He had written that he "felt sure he had caused a UFO scare on one occasion".

So, here's how to do it - how to provide a convincing imitation of an Unidentified Flying Object. Don't try this at home, kids.

For this trick, you need a night with completely clear skies - no cloud to form a visual reference - and with no moon to provide undesirable illumination.

Pick a time of year when the jet streams are blowing strongly - you know, those fast-moving stratospheric air currents that the pilots of commercial airlines like to blame for their late arrival. Wintertime is preferred. Oh, and you'll need a military jet. My Dad did this in a Canberra, but I dare say that any modern jet fighter would work just as well.

So, off you go. Fly up to 45,000 feet over some major conurbation, and head into the wind. Now, the jet streams are probably running at around 150 knots, so you throttle back until your airspeed is about one-fifty. From the ground, you are now more-or-less stationary. If you're equipped with a radar ground speed indicator, you can fine-tune your direction and airspeed until you are completely stopped, just hanging in the air.

Then, you turn on all the landing lights. These lights are typically distributed fore-and-aft, and on the wing-tips, and around the undercarriage. So, from the ground, you look like a disk with illuminated portholes, or engines, or whatever, all around the circumference.

You sit there in the jet stream for ten minutes or so, chuckling with your co-pilot about the stir you're probably causing on the ground. What a wizard wheeze. Then, you turn about and throttle right up, so that you are streaking through the skies. Then, just when you've reached your maximum speed, turn the lights off again. Your observers have just seen a hovering object suddenly accelerate from rest to a phenomenal speed - "no known aircraft can fly like that" - and then disappear.

Now you're a UFO. Good, huh? With a bit of luck, your appearance and sudden disappearance will be reported in the more sensationalist newspapers with banner headlines, and some no-doubt anonymous government spokesman will be quoted in the small print explaining that this was a just "an ordinary unscheduled military training flight".

Now my old Dad has something of a reputation as a prankster. He's always ready with a joke or two, often highly politically-incorrect and downright filthy, but usually irresistibly funny for all that. He was the editor of the Rotary Club newsletter, which also gave him an outlet for his personal sense of humour and, since he was a bit of a Silver Surfer, he had taken to trawling the Internet for humorous material. I would occasionally send him 'funnies' in the electronic mail which I feel sure became newsletter material and I would often get something hilarious in return.

Having re-read the words from his book, I had simply assumed it was a practical joke, a lark. I tackled him on the topic during one of my inexcusably infrequent visits.

We were sitting in the small but well-maintained garden at the back of the house last summer, basking in the early evening sunshine and enjoying a glass of sherry before dinner. My wife was occupied elsewhere in the house with our children. My mother was busying herself in the kitchen, producing one of those splendid roast dinners I remember so well from my childhood, but which I feel I must resist most of the time these days, if only to keep my weight and blood pressure down.

Dad went uncharacteristically quiet for a few moments. Then, in low and serious tones, he told me what actually happened on that night back in the fifties, an episode which occurred before I was even born. He made it clear that this was not a prank, a whim, but that he had been specifically instructed to go up and perform this trick.

Canberra aircraft on the ground I already knew that, for many years, my old man was a pilot instructor and flight examiner, flying Canberras. He had countless old comrades and acquaintances that he had met in the service, many of whom he had actually trained at one time or another. Night training flights were a standard part of the instruction programme, an essential part of the military role to be able to be airborne at any time and under any weather conditions.

He reminded me that there was a three-man crew for these early-version Canberras - a pilot, a co-pilot and a navigator-bombardier. These aircraft were equipped with twin controls, highly suitable for pilot training - indeed, Dad had done his own jet training in one of these aircraft not so long ago.

My father explained that, on the night in question, the routine pre-mission briefing for what was originally a standard night training flight was unexpectedly interrupted by the Wing-Commander himself. The Wingco was a RAF officer of the old school, right the way down to the ginger handlebar moustache. He had served with distinction during the war and was widely regarded as one who did not suffer fools gladly.

On this occasion, the Wingco seemed extremely annoyed at the disruption and the sudden change of plan, though my father thought he had detected an undercurrent of nervousness uncharacteristic of the Old Man.

The Wingco was accompanied by three other men, two of whom were not wearing any kind of uniform but nevertheless had the bearing of military men. Dad never did discover the origins of these two men, but he strongly suspected that they were from the US Central Intelligence Agency. At that time, CIA pilots were required to resign their military commission at the time of joining the Agency, a process wittily known as 'sheep-dipping'.

The third man was in the uniform of the US Air Force. This in itself was not unusual; the RAF maintained a close collaboration with the Americans at this time. In those Cold War days, there were American airbases all over Southern and Eastern England, many of which were reputed to house air-delivered strategic nuclear weapons. As a child, I clearly remember disparaging remarks being make by my father, when passing by in the car, about the bra-less anti-war protesters at Greenham Common with their "ban the bomb" slogans and CND posters.

Of course, in spite of the close collaboration, there was a certain amount of friendly (and occasionally not-so friendly) rivalry between the air forces. My Dad summarised it thus: the Americans considered the RAF tiny and under-equipped to the point of irrelevance, while the Brits found the erstwhile colonials both arrogant and unwilling to take risks.

The USAF officer took immediate charge of the training briefing, leaving the Wingco fuming at being required to do nothing other than to lend his authority to the instructions being issued by the American.

The trainee pilot was quietly but firmly instructed to return to barracks. His place on the mission was replaced by an unsmiling man my father was instructed only to refer to as Rex, one of the officer's near-silent companions in mufti. The navigator was retained, although it turned out that his role was very limited, since they wouldn't be flying very far. Dad said that he was killed a few years later in a freak accident, one which was never satisfactorily explained.

At the time, the Canberra was one of the few aircraft capable of flying extremely high - well above the heights achieved by modern commercial jets. My father pointed out that this aircraft was designed as a Cold War bomber, capable of delivering nuclear weapons to foreign capitals whether they wanted them or not.

Early versions of the aircraft had a service ceiling of 48,000 feet, but in the late fifties, Canberra variants set a series of height records, in one case in excess of 70,000 feet. In fact, I understand from Dad that the official maximum height for late-model aircraft is still officially restricted information.

Of course, there were a very few other aircraft then capable of reaching these kinds of height. Dad had heard rumours of a classified aircraft he later discovered to be the Lockheed U-2 spy plane, which was by then in service with the CIA, flying intelligence missions over potentially hostile foreign soil. The U-2 could travel higher and further than the Canberra, but had a reputation of being tricky to fly and with difficult - even dangerous - handling in poor weather conditions.

The point is that there was very little else up there - still isn't, really. All modern subsonic commercial traffic is at 40,000 feet or below and, now that Concorde has been grounded, anything you see at that height is likely to be military in origin.

Introduction Part 2