'Evidence of life in space is tough to uncover as there may be only one in each galaxy' says Nigel Nelson

The British Government says it might hold an investigation of its own but is awaiting the outcome of American deliberations. Former MoD UFO investigator Nick Pope told me he reckons we should, and his X-Files team, started by Winston Churchill in 1953 and abandoned by 2009 defence cuts, should be reformed.

He said: “UFOs have come out of the fringe and into the mainstream. They are no longer regarded as science fiction.

“US Navy top guns have chased the mystery intruders in their jets, and recorded the objects on their forward-looking infrared cameras.

“I support re-opening the real-life X-Files. If there’s anything unidentified in our airspace, it should be treated as a defence and national security issue.”

Rock ‘n roll TV physicist Brian Cox agrees. He estimates there could be 200 billion alien civilisations in the universe. But evidence of intelligent life in space is tough to uncover because there may be only one in each galaxy - and us Earthlings fill the Milky Way’s quota.

You can test the possibilities yourself. Pick up a fistful of sand from the beach and you will have a million grains in your hand. Now look up at a night sky. Beyond the pinpricks of light you can see there are more stars out there than in all the sand on all the beaches of all the world. Many will have solar systems, and some could contain planets similar to Earth.

Which means a high statistical probability there is life like us elsewhere. But when we talked about his recent BBC documentary on this, Professor Cox cautioned to be careful what we wish for. “We’d all like ET to be real,” he said. ”We’d like ET to arrive. But we don’t want Darth Vader coming down.”

The Pentagon has been collecting evidence from the likes of US Navy fighter pilot Lieutenant Commander Alex Dietrich about her own UFO close encounter on November 14, 2004 when she was stationed aboard aircraft carrier USS Nimitz off California.

The ship’s radar detected flying objects dropping through the sky at an unbelievable 80,000 feet in less than a second. She and Commander David Fravor were scrambled in their F/A-18 jets and came across what they describe as something looking like a 40 foot long white Tic Tac.

She told the US news show 60 Minutes: “It jumped from spot to spot, and tumbled around in a way that was unpredictable. The whole time we’re on the radio with each other just losing our minds.”

Dave Fravor added: “I wanted to see how close I could get. And when it got right in front of me it just disappeared.”

Former Navy pilot Lieutenant Ryan Graves said his F/A-18F squadron began seeing UFOs hovering over restricted airspace southeast of Virginia Beach in 2014 and again off Florida the following year. He said: “You have rotation, you have high altitudes. You have propulsion. I don’t know what it is, frankly. “

Even former president Barack Obama told talk show host James Corden: “There’s footage and records of objects in the skies that we don’t know exactly what they are. We can’t explain how they moved.”

Prof Cox said the 42 radio telescopes operated by SETI - the Search for Extra Terrestrial Intelligence in northern California - have only picked up one 72 second signal burst which came from the Sagittarius constellation 10 light years away on 15 August 1977 and arrived on a wavelength SETI believes an intelligent civilisation would use.

He added: “We’ve heard nothing since. That could be because intelligent life is extremely rare and you have to be in the right place at the right time to hear it. If only we had sensitive enough detectors we may be able to pick up more signals.”

This makes sense. Edinburgh University astronomer Beth Miller points out that contact with aliens would only work if their civilisation exists around the same time as our own. And it would have to be close by in cosmic terms because we have only had the technology to pick up radio signals for the last 100 years.

So if aliens 40,000 light years away had been trying to get in touch 30,000 years ago the message would have been sent when Neanderthals still walked the Earth. But no matter. Travelling at the speed of light it will still not arrive for another 10,000 years so we haven’t missed it.

But Nick Pope said: “If those messages were able to find their way around the lightspeed barrier they could appear here in an instant.”

Lue Elizondo joined the Pentagon UAP programme in 2008 after 20 years running intelligence operations in Afghanistan and the Middle East. He said: “Imagine a technology that can fly at 13,000 miles an hour, fly through air and water and possibly space.

“And it has no obvious signs of propulsion, no wings, no control surfaces and yet still can defy Earth’s gravity. That’s precisely what we’re seeing.”

In most cases meteors, satellites, weather balloons or Venus are mistaken for flying saucers. But Elizondo added: “There are some that are not.” And Nick Pope reckons of all the sightings he investigated five per cent defy any conventional explanation.

But the House hearing is arguably being undermined by some extraordinary and outlandish testimony. Retired Air Force Major David Grusch claims the US has covered up its possession of “intact and partially intact” alien vehicles and has hoovered up body parts from crashed wreckage. This has infuriated Pentagon intelligence chiefs who say he is spouting rubbish.

Whenever I speak to senior British spooks the one question I always ask is how many really big secrets MI5 and MI6 might be concealing which would knock our socks off if we knew about them. The consensus seems to be around half-a-dozen, though, of course, they won’t tell me what they are.

But I have always wondered if evidence of aliens could be one of them.