By Jane Corbin BBC Panorama reporter

The convoy of jeeps meandered through the gorge en route to Jalalabad, the scene of Osama Bin Laden's last public appearance.

It's the most dangerous road in the world, where four journalists had been hauled from their vehicles and brutally murdered only a few months before.

This is bandit country, in one of the world's most lawless regions - the perfect territory for Bin Laden to hide after the atrocities of 11 September.

I had come to Afghanistan after following the career of Bin Laden since 1997.

In that time I had interviewed scores of people whose life had been touched by him - from fellow mujahideen who had fought with him against the Soviet invaders, and who attested to his bravery and generosity, to those whose lives had been ripped apart by cowardly explosions carried out by his al-Qaeda organisation.

Hour of reckoning

Bin Laden has evaded the west so far

It was in Jalalabad on 10 November that Bin Laden gave his last address in public at the Islamic Studies Centre.

The war was not going well for the Taleban, his hosts in Afghanistan, as the US-backed Northern Alliance closed in on Kabul.

Bin Laden sensed that the hour of reckoning was nigh, and nervously told his followers to carry on the fight.

And then he fled, in a convoy like ours, heading south to the Spin Gar mountains and his favoured cave complex of Tora Bora.

Treachery

His trail was picked up by the American and British special forces on the ground. In this part of the world, treachery is rife.

As Major General Hagenbeck , the chief of the Allied Forces in Afghanistan wryly commented: "You can't keep a secret in Afghanistan".

But just as you can't keep a secret, don't expect to be able to trust the local allies who may be working for you.

former mujahideen were keen to do their dirty work... or rather, were keen to take the dollars

This was the first lesson that the Americans learnt in the war on terror; Bin Laden was holed up in Tora Bora while the allies were homing in on their prey.

But rather than commit their own troops to the ground, they used former mujahideen who were keen to do their dirty work for them; or rather, were keen to take the dollars that were proferred them.

Escape

Bin Laden escaped over the border into Pakistan. Hazret Ali, a former mujahideen now fighting the al-Qaeda at Tora Bora, conceded that there had been some dishonesty, in a part of the world where Bin Laden was very popular.

Jane Corbin on the trail

As he told Panorama, "All the mujahideen in this area were involved.

"It was difficult because, especially in the Tora Bora area, all of them were friends with Osama, he gave weapons to people, he paid money to them, all the houses here in the mountains co-operated with Osama.".

And so the world's most wanted crossed the border into Pakistan, into the lawless reaches of Waziristan, and the trail went cold.

The Americans learnt their lesson. If they were to destroy Al Qaeda and capture Bin Laden they had to commit troops to the ground.

They turned to the former Soviet Airbase of Bagram, an hour north of the capital Kabul, and drafted in thousands of troops.

The programme tells the story of what happened next, and how the world's most wanted man gave the world's superpower the slip.