Was I going to ask him about "terror"? No, I wanted to know what it was like to fight the Russians. A Soviet mortar shell had fallen beside him, Osama bin Laden said. Nangahar province, maybe 1982.

"I felt seqina as I waited for it to explode, " he said. Seqina means an almost religious calmness. The shell - and many must curse it for being a dud - did not explode. Otherwise Osama bin Laden would have been dead at 25.

When I met him again in Afghanistan in 1996 he was 39, raging against the corruption of the Saudi royal family, contemptuous of the West. When Saddam Hussein invaded Kuwait in 1990, bin Laden told the House of Saud that his Arab legion could destroy the Iraqis; no need to bring the Americans to the land of Islam's two holiest places.

The king turned him down. So the Americans were now also the target of Osama's anger.

Has he grown wiser with age? The next year, he told me he sought God's help "to turn America into a shadow of itself". I wrote "rhetoric" in the margin of my notebook - a mistake.

Age was giving bin Laden a dangerous self-confidence. But as the years after 11 September 2001 went by, I watched the al-Qaeda leader's beard go grey in the videotapes. He talked about history more and more: the Balfour declaration, the Sykes-Picot agreement, the end of the Ottoman caliphate. His political speeches appealed to Arabs whose pro-American dictators would never have the courage to tell George W Bush to take his soldiers home.

There was no contrition. Age - if it bestows wisdom - did not allow bin Laden to question his own motives, to express any self-doubt. In the tapes, his robes were embroidered.

He appeared like a mahdi, a seer.

But I wondered, as the years went by, if he was any longer relevant. Nuclear scientists invented the atom bomb.

What would have been the point of arresting all the scientists afterwards? The bomb existed. Bin Laden created al-Qaeda. The monster was born. What is the point, any longer, in searching for 50-year-old Osama bin Laden?

Five years ago, Time magazine offered to buy one of my photographs of bin Laden in Afghanistan for its front cover. I refused to sell it. Time wanted, so their picture desk told me, to use a computer to 'age' bin Laden in my snapshot. Again, I refused.

"So how much do you want?" the Time picture desk asked. They didn't understand. Bin Laden may have no integrity, but my pictures did:

they showed a man in his 30s and 40s, not in his 60s or 70s.

But now he is turning 50. I don't think he'll be celebrating in his cave.

Just reflecting that, white-flecked though his beard now is, he remains the West's target number one, as iconic as any devil, so embarrassing to Bush that the US president no longer dare pronounce his name, lest it remind his audience that, even in middle age, bin Laden is the one that got away.

I read the 'experts' telling me that bin Laden has cancer, that he needs medical machines to survive. But we say this about all our enemies. Bin Laden now uses a stick to walk - unusual for a man of 50 - but we know he was wounded in Afghanistan. The truth is - and forget the 'experts' who might tell you otherwise - that bin Laden is still alive. Like the Scarlet Pimpernel he may be damned and elusive but he remains on this earth. Aged nearly 50.