Click here to listen

It strikes me with the shock of a suddenly tolling bell that there may be listeners today who are saying: "Colonel who?"

Well to be brief and downright at the start let me say that on February 19 or 20, 1962, nobody in the world outside the United States and inside it only a few American politicians, air force men, the staff of a new mysteriously-named National Space Agency had ever heard of him either.

Overnight he became suddenly the most famous man in the world. Nothing in our time, nothing this century, had been like it. Ah yes, there was, there had been.

The only other time such a miraculous lightning stroke of fame had produced an overnight worldwide hero was 71 years ago. When a young, early airmail pilot - very primitive trade - we're talking about the spring of 1927, a totally unknown Midwesterner took off on a drizzly day from a muddy field on Long Island in a single engine propeller plane, missed the telephone wires by a few feet and was off east into the skies on the frightening enterprise of becoming the first man to fly the Atlantic alone.

Before him the only people who might have heard about such an enterprise would have been people who read newspapers. But in 1927 radio had circled the globe. Everybody had it - except Mr Lindbergh in his plane. So the first time we'd know about him or how he was doing would be when somebody on land saw this midget plane in the air.

During the night, when his plane must be - we hoped - somewhere over blue water, 40,000 baseball fans in New York stood and prayed for him. Stock exchanges in six countries interrupted their quotations with the word - that there was no word.

By that time, I suppose, every newspaper on Earth was hanging by its inky fingernails onto the story. Second night came on and the Paris radio urged everybody who owned a motorcar to head for a landing field known as Le Bourget, line up in two files, switch on their headlights and thus create a very crude glide path - nothing better than a visible shaft of fog.

Thirty three hours after he'd wobbled off that muddy Long Island field he spluttered, trundled and stopped and 100,000 Parisians engulfed the field, pulled a dazed 25-year-old out of his plane. He said: "I am Charles Lindbergh".

For a pandemic of nervous tension being felt by millions around the world about an unknown American nothing obviously would ever touch it in our time. But it did. Thirty six years ago last February.

And we're about to uncover the identity of this other obscure Midwesterner who - but at the age of 41 - also was to become, overnight, the most famous man on Earth or above it.

John Glenn was born in Columbus Ohio in 1921, graduated from a small college and 20 months later he knew what he wanted to do: to be a naval aviator. He became a cadet, he graduated from flight school, was in the last year of the Second World War in the Pacific with the Marines Aircraft Wing. Then in the Marshall Islands Campaign, fought in the Korean War as a fighter pilot.

When that was over he joined this new and to most of us spooky-sounding outfit called the National Aeronautics and Space Administration - Nasa - as it came to be called.

The space programme cast a magical spell even before anybody had gone into space. But even now throughout the 30 odd years that many men and women of several nationalities have worked in space, have lived in space for months, question anybody between 20 and 90 for an instant response to the challenge - name a space hero - the name that comes at once to mind is John Glenn.

Now you could have asked, even at the time, what was so special, so magical, about John Glenn? Since a year before him a Russian, one Yuri Gagarin, was the first human to orbit the Earth in space and four months after him another Russian did it 17 times.

Well we believed the Russians did it - the point is we didn't see it, we saw their General Secretary of the Party kiss Gagarin on both cheeks. They were on the ground at the time after the whole show was over. And we took the Russians' word about him and about the other, the 17-timer. But in those days the Russians were as tight-lipped and uncommunicative, when they were head man of the Soviet Union, as the Chinese are today.

I wonder if anybody remembers a talk I did years ago about an earthquake in China - must be oh 20-odd years ago? The Chinese said: "Thanks but we need no help from capitalist imperialists, there are a few thousand dead and we can manage on our own". It came out later, the fact: there were a quarter of a million dead.

So the searchlight that exposed John Glenn to world fame in four hours and 56 minutes was the simple existence of television and the willingness of the American government to show the whole adventure. Let us see what could be seen and hear every exchange - intelligent, dumb, stumbling, anxious, whatever - between the Houston Space Centre and John Glenn up there going for three orbits.

Our television had always in view an accurate model of Glenn's capsule and him squeezed into a cockpit not wide or long enough to let him even wriggle. He lay on his back throughout.

And when trouble developed we heard the cryptic dialogue and we heard the marvels of the deep skies when Glenn said: "Oh boy, oh boy" when a tidal wave of particles of light swam by him like fire flies. And later he gave a warm cry of thanks to all the people of Perth in Australia who'd turned on the city lights by night and spread sheets and blankets on roof tops as reflectors.

You have to remember all we knew about space flight was what some awe-stricken movie producer had imagined it to be. Here listening to the nervous exchanges between Houston and Glenn our own fears of the unknown were soon heartfelt when, after two orbits, a warning light came on - what was that? He'd used up his gases too fast, he'd have to fire the gases electrically and steer the ship by hand. Dare they let him go for a third? They did. It worked fine. And the thousands packing railway stations around America and cab drivers and nurses and families leaning into radios around the world breathed again.

On the third orbit there was the final and it appeared, probably, fatal ordeal. There was fastened to the nose of the mushroom-shaped capsule something called a heat shield. It was constructed to withstand the 3,000 degree heat which flares up when the capsule rips back into our atmosphere. Half way through the third orbit Houston saw signs that the shield was coming loose. A warning light in his capsule said so.

They didn't tell Glenn. He thought the switch was simply on the blink. They ordered him to fire the rockets to shoot home to Earth but to hold on to what had been their protecting package. They hoped for the best.

There was a crackle of static and nothing from Glenn for two and a half awful minutes. Perfectly all right, we learned later, because once the capsule enters the ionosphere there's so much ionisation that no radio frequencies can get through anyway. Then came in the voice of Glenn and sent five continents into cheers.

Back on Earth Glenn said he'd seen chunks of flame going by his window and he knew as well as Houston that if it was the heat shield burning up he would burn to a cinder in a second or two. It was, in fact, the rocket package burning up.

He said: "I became supersensitive along my backside. It gave me a moment of some concern".

For the next year or so the fame that overwhelmed John Glenn made any stroll in public an agony. If presidents were elected by public referendum he could have abolished the Constitution and been proclaimed president overnight.

However, the more extreme is popular idolatry, you may have noticed, the quicker it fades except, don't tell me how or why, for Elvis.

John Glenn went into politics. For 24 years he was a senator from Ohio and, need I say, most prominent and influential on bills about space, defence. And as time went by he became more and more interested in space medicine. What space flights, or the people on them, can find out about the human body.

John Glenn appealed to Nasa about a year ago to let him go up once more to be used as a guinea pig to see what space pressure or lack of gravity does to ageing, or rather: Would it explain the long known and demonstrated fact that the moment an astronaut gets out of the pull of gravity, the body at once takes on all the deteriorations of old age, notably bone and muscle loss, shrinking of the heart and a weakening of the heart muscle?

There are, I assure you, about 20 other symptoms that most people who get beyond 80 know about, if not enjoy. John Glenn is 77 and he has, for most of the past year, gone through a crucifying training routine that would finish off most men in late middle age.

Among the many risks that his flight entails is the special one, even for a man fight at 77, that it might be too much for him.

He told one anxious technician: "Don't pray for my safety, pray I'll be useful".