ZINTAN, Libya, Nov 20 - Saif al-Islam Gaddafi, who was captured in Libya's rugged desert, transformed himself during this year's uprising from a relaxed reformer to a belligerent and loyal lieutenant of his father who is now wanted by the ICC accused of crimes against humanity.

Saif al-Islam, the late Muammar Gaddafi and his spy chief were charged by the International Criminal Court over the bloody military crackdown on the popular revolt that erupted in February as part of the shockwaves that jolted the Arab world.

In his final days on the run, witnesses said Saif al-Islam, 39, was nervous, confused and frightened, at first calling his father by satellite phone, swearing aides to secrecy about his whereabouts and, after his father was killed, seeking to avoid a similarly gruesome fate.

There had been fears that, aided by Tuareg tribesmen who had benefited from Gaddafi senior's largesse during his 42 years in power, he could hide indefinitely in the mountains that straddle Libya's borders with Niger, Algeria and Mali.

Saif al-Islam - a name which translates as the sword of Islam - had vowed to go down fighting.

But in the end, the graduate of the London School of Economics was captured, nursing a hand wound, without a struggle.

Abdelsalam - or servant of peace - he replied when asked his name by fighters from the mountains of Zintan who stopped him in the dead of night in the desert. They quickly recognised a man whom many assumed had been set to continue a dynasty founded by his father in a military coup before Saif was born.

On the plane that took him to an uncertain future in the town of Zintan on Saturday, a robed Saif al-Islam first hid his face and dodged questions from a Reuters reporter on board. He later confirmed he was okay and said his hand had been injured in an earlier NATO air raid.

After landing, hundreds of people crowded around the aircraft, shouting Allahu Akbar (God is greatest), trapping him inside for more than an hour.

Many Libyans believe Saif al-Islam knows the location of billions of public money stolen by the old regime - but when detained, his captors said, they found only a few thousand dollars.

The only one of Muammar Gaddafi's eight children who had been still on the run, Saif al-Islam had offered to surrender to the Hague-based ICC but some officials there feared this could be a bluff and warned mercenaries with him that if they sought to escape by aircraft they could be shot down.

There had been some dangerous moments for Saif al-Islam. He escaped even though his motorcade was hit by a NATO air strike as it left the town of Bani Walid on October 19, the day before his father died in his hometown of Sirte.

Once seen as an internationally well-connected philanthropist and reformer said to be behind negotiating an end to Libya's nuclear and chemical weapons programmes, Saif al-Islam turned abruptly into a soldier when the rebels rose up against his father.

WE DIE HERE IN LIBYA

The ICC accuses Saif al-Islam of recruiting mercenaries to carry out a strategy, worked out with his father and intelligence chief Abdullah al-Senussi, to kill unarmed protesters who were demanding Gaddafi go.

We have a witness who explained how Saif was involved with the planning of the attacks against civilians, including in particular the hiring of core mercenaries from different countries and the transport of them, and also the financial aspects he was covering, ICC prosecutor Luis Moreno-Ocampo told Reuters.

The man the West had seen as a liberal reformer and architect of rapprochement exploded with belligerent rhetoric when he swore to crush the protests.

We fight here in Libya; we die here in Libya, Saif al-Islam told Reuters shortly after the rebellion broke out in February. He called the protesters rats.

Three of Gaddafi's sons did die on home soil, along with their father, whose battered and abused body went on public show in a meat store before its burial in October.

Saif al-Islam was viewed by many governments as the acceptable, Western-friendly face of Libya, and heir apparent to his father. But when the rebellion broke out, he chose family and clan loyalties over his many friendships in the West.

As Tripoli fell to rebels in August, the ICC prosecutor announced he had been arrested, opening the way for his extradition. But this was premature and he popped up at a Tripoli hotel used by foreign journalists to prove he remained a free man.

BREATHING DEFIANCE

I am here to disperse the rumours, he said, pumping his fists in the air, smiling, waving and shaking hands with supporters. The ICC later said it had never received official confirmation of Saif al-Islam's capture.

Gaddafi's four other surviving children -- three sons and a daughter -- are in exile in neighbouring Algeria and Niger.

Outgoing Libyan Prime Minister Mahmoud Jibril told Reuters this week he was still concerned that Saif al-Islam could mount attacks on the fragile new administration while on the run.

But analysts doubted Saif could lead a serious insurgency, saying his influence was much reduced with his dominating and intimidating father now dead.

The answer really is a big 'no'. Saif rose to prominence by virtue of being his father's son, said Jon Marks, chairman of the consultancy Cross Border Information, before his capture.

Ironically, his biggest boosters during the 'Saif years' -- when he was prominent but perhaps never dominant given his father's leading role pulling the strings -- are the very governments and politicians who ended up bombing his regime into oblivion.

Before the rebellion, Saif al-Islam sometimes appeared genuinely at odds with Gaddafi senior, who ruled for four decades through fear and violence.

Mainly through his charitable Gaddafi Foundation, Saif al-Islam pushed for reform, including more media freedom, acknowledgement of past rights abuses and the adoption of a constitution. He also oversaw a reconciliation with Islamist rebels who launched an insurgency in the 1990s.

But his efforts were stymied by opposition from inside the ruling elite and - some analysts say - from members of his own family. Last year, the independent newspaper he had helped to found was forced to mute its criticism of the authorities and his foundation withdrew from political activities.

ON THE INTERNATIONAL STAGE

One of his projects did succeed, albeit one that suited his father. He played a central role in negotiating the lifting of U.S. and European sanctions on Libya in 2004, in return for Tripoli ending its nuclear and chemical weapons programmes.

This led to Britain's then-premier, Tony Blair, visiting Tripoli to embrace Gaddafi senior, long a pariah in the West.

Saif al-Islam owned a 10-million-pound ($16-million) home in London but his activities and friendships caused much embarrassment in the West when the rebellion broke out.

The director of the LSE, Howard Davies, resigned over the university's ties to its former student.

The LSE had accepted a 300,000-pound donation from Saif al-Islam's foundation, a decision that Davies said had backfired. The LSE also investigated the authenticity of Saif al-Islam's PhD thesis, which was awarded in 2008.

Like his flamboyant, eccentric father, Saif al-Islam had cultural aspirations. On a mission to put Libya on the artistic map, he exhibited his own paintings around the world, some of which were lampooned by critics in an exhibition called The Desert Is Not Silent.

One, entitled The Challenge -- painted during the period of the embargo against Libya when the West accused it of international terrorism -- showed Muammar Gaddafi gazing down from the skies at the arrogant Allies bearing wooden crosses. Others pictures depicted the Bedouin tents favoured by his father.

Jonathan Jones, art critic for Britain's Guardian newspaper, said the paintings just end up confirming all the old stereotypes about dictators, or dictators' sons.

Ever since Nero there has been a depressing connection between bad art and megalomaniac regimes: Hitler the opera lover, architect and painter; Stalin the poet, Jones wrote in August this year.

(Additional reporting by Alastair Macdonald in Tripoli; Writing by David Stamp and Peter Millership; Editing by Andrew Heavens)