ON A cold Monday morning 22 years ago, Jean-Jacques Velasco was sitting in his office when a gendarme rang to tell him about a strange incident. Renato Nicolai, a retired technician, had been working in his garden in Trans-en-Provence, near Nice, when he saw a dark, round object come down from the sky, settle on the ground and take off again, the gendarme said.

Over the years, Velasco has heard many such stories, and disproved most of them. But this one was different — this one was credible, he believes. Something seems to have landed in Trans-en-Provence, he says, and that something has never been identified.

But who is Velasco? Another crackpot determined to find a flying saucer? A follower of Claude Vorilhon, the Frenchman who founded the Raelian sect amid claims that he was the son of an extraterrestrial being? No, he is a scientist working for the state-run National French Centre for Space Studies (CNES), where he heads a department responsible for analysing what are commonly called unidentified flying objects (UFOs) but what are officially known as unidentified aerospace phenomena (UAP).

It is a unique department, the only permanent government-financed scientific project set up by a developed country to unravel fact from fiction in the debate about UFOs.

In an area that draws the deranged and the dreamers, this is a serious research programme. “We have shown that there is a category of events that are not part of the classical physical scheme of things,” says Velasco. These may be a light, or an object moving across the sky on “an abnormal trajectory”, sometimes noiselessly.

“In some cases, there is a feeling that the phenomenon is adapting its behaviour to the environment. In others, people claim to have seen small material objects very close to them, which may even land. In the most extreme cases, people claim to see objects with beings next to them.”

A neatly-dressed, bespectacled man, Velasco talks with the careful precision of an academic who is keen to be understood. He is not saying that he has come across visitors from another planet; he is saying merely that events occur for which science has yet to find an explanation, and which merit further inquiry.

“Two hundred years ago, the French Academy of Science said meteorites did not fall to Earth, that the phenomenon did not exist,” he says. “Now we know it does.”

Velasco’s department was set up in 1977, the year that Close Encounters of the Third Kind was released amid a global UFO fever. Across the world people thought they saw strange figures, flying saucers and bright lights. Sects such as the Raelians claimed to be in contact with extraterrestrial life. And amateur associations pledged to shed light on the burning question: are we alone? But there were few serious attempts to probe the issue. The US authorities had studied it ten years earlier and concluded that it was a waste of taxpayers’ money. Most other countries, including Britain, thought likewise. Only France took the matter seriously, partly because it has the centralised state apparatus necessary to do so, and partly, no doubt, because of a vainglorious belief that if a UFO is to be found, France should be the one to find it.

The CNES duly set up the Service for Expert Appraisal of Atmospheric Re-entry Phenomena (Sepra). Based in Toulouse, the department is as pedantic as its title sounds: the staff are state-employed scientists, shaped by a prudent, rigorous and somewhat bureaucratic culture. In France such bureaucracy can often be cumbersome and painfully rigid. Yet in this domain at least, this rigidity offers a guarantee of impartiality that is rare as far as UFOs are concerned.

Last year, when the CNES was told to reduce its €1.3 billion (£853 million) budget, the organisation’s president, Alain Bensoussan, ordered an audit into Sepra’s work. A wide range of French scientists was asked whether it was worth continuing research; almost all said yes.

One reason is because, unlike most other UFO-hunters, Sepra’s staff are neither seeking publicity nor peddling an obscure belief in extraterrestrial civilisation. They say they do not know whether extraterrestrial beings exist or not, and look disparaging when you ask them to voice their hunches on the question.

They do not have hunches, only statistics. Yet the statistics that Velasco has made public are eloquent. Since, 1977, Sepra has received some 6,000 reports of alleged UFO sightings. Of these, 110 are from civil or military aircraft crew, and the rest from ordinary French people who have almost invariably contacted their local gendarmerie. In 21.3 per cent of cases there is a clear, indisputable and banal explanation: a firework display, a novel lighting system involving a luminous balloon, a cloud above the Pyrenees that is shaped like a flying saucer. In 24.9 per cent there is a probable explanation, and in 41.3 per cent the information is too vague to be of use. But in 12.5 per cent of cases — about 750 sightings since 1977 — the evidence is precise, detailed and inexplicable, and is thus categorised as an unidentified phenomenon.