Watch seven-year-old Abdelkahar Belhadj address a political rally
One of the most remarkable archive sequences we came across while researching the Age of Terror programme, features a seven-year-old Algerian boy called Abdelkahar Belhadj. He is seen addressing a political rally of thousands in 1991 with all the confidence and fire of a mature adult.
"There are a billion Muslims and we don't have a state that rules by God's Holy Law. Isn't that a dishonour and a shame on us?" he proclaims in the voice of a child.
He is cheered ecstatically and lifted on high. It was revelatory to hear the philosophy of jihad - the struggle to overthrow infidel regimes and replace them with Islamic states under Sharia law - emerging from the lips of one so young.
In 2007, 16 years later, we watched another clip, a propaganda video announcing the launch of al-Qaeda in North Africa featuring non other than Abdelkahar Belhadj, now a fully-fledged jihadi.
The letters IRA are visible on Sean's left hand
When I first saw the clip of the young Belhadj, I was instantly reminded of an interview I'd done in an IRA stronghold in Belfast in the mid-seventies with a little boy called Sean. I vividly remember he had the initials IRA inked on the back of his hand.
Sean told me he wanted to fight and die for Ireland. Years later I met him again, this time on an IRA wing inside the Maze prison. He had gone to jail after fighting for the cause he had embraced all those years ago.
Sean and Abdelkahar Belhadj illuminate the bigger picture of the Age of Terror: how the "cause", be it Islamist or Republican, Basque or Palestinian, flows from one generation to the next and on through the veins of history.
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Age of Terror: The Paris Plot, presented by Peter Taylor, is on BBC Two at 9pm on 29 April
Abdelkahar Belhadj was a third-generation jihadi. His grandfather was a shaheed - a martyr in Algeria's bloody war of independence in which the insurgents of the National Liberation Front (FLN) finally won freedom from French rule.
His father, Ali Belhadj, was number two in the Islamic Salvation Front (FIS), a loose coalition of Islamist political parties that coalesced at the beginning of the 1990s to challenge the corrupt and discredited FLN government that had ruled Algeria since independence.
When Abdelkahar made his remarkable debut as a seven-year-old firebrand, his father was in jail serving a 12-year sentence for armed conspiracy against the regime.
Ali Belhadj, a charismatic Islamist preacher had done much to radicalise Algeria's disaffected youth.
By the late 1980s, 40% of the country's population of 24 million were under the age of 15. Many were in school preparing for jobs that did not exist.
In the ensuing confrontation, the army shot dead 50 demonstrators. It was Algerian's equivalent of Northern Ireland's "Bloody Sunday" or South Africa's Sharpeville and Soweto.
They became known as hittistes - "those who prop up walls" - as they had nothing else to do all day.
They were angry and frustrated, providing the rich soil in which a brand of militant, fundamentalist Islam could flourish.
Neighbourhood mosques became the focus for discontent with clerics building support not just through fiery sermons but through practical support, running soup kitchens and providing food, clothing and welfare.
In 1988, Algeria exploded in the month known as Black October. Ali Belhadj organised a demonstration of 20,000 Islamist supporters who were stopped in their tracks by the military that effectively ran the regime.
In the ensuing confrontation, the army shot dead 50 demonstrators. It was Algerian's equivalent of Northern Ireland's Bloody Sunday or South Africa's Sharpeville and Soweto.
The fuse was lit. Algeria's intifada had begun, the launchpad for political Islam.
In 1991, to try and head off further violence, the regime agreed to free multi-party elections, for the first time since independence.
The result of the first round shocked the government, which had fatally underestimated the growing strength of the Islamist parties. The Islamic Salvation Front won the first round with a clear majority.
The regime panicked and cancelled the final round, fearing with good reason that the Islamist opposition was likely to win.
The Islamists, who did not believe in parliamentary democracy, had made it clear that once in power there would be no more multi-party elections, as the state would thereafter be governed under Sharia law.
Terrorism grew out of the anger and frustration that followed the government's cancellation of the election. Cadres of militant Islamists coalesced as the GIA, the Armed Islamic Group, became convinced that political Islam had failed and violence was the only way to effect change.
They had recently seen many Algerian mujahideen playing a significant part in the jihad that had succeeded in driving the Soviet Union out of Aghanistan in 1989. Why could the Algerian regime not be confronted and toppled in the same way?
Algerian veterans returning from Afghanistan drove the message home.
Air France hijack
The years between 1993 and 1997 are among the most bloody in Algeria's tortured history.
Paris was the target of the Air France hijackers in 1994
Ten thousand are estimated to have died. The GIA embarked on a horrific campaign of indiscriminate violence: so-called collaborators were beheaded and disembowelled, intellectuals and teachers were picked out and killed and whole communities were massacred. In 1997 in the village of Benthalla, 200 were beheaded in one night.
The state retaliated with awesome ferocity setting loose the 15,000 soldiers of its feared anti-terrorist force known as the Ninjas.
The hijacking of Air France flight 8969 with over 200 passengers on board on Christmas Eve 1994 - the subject of The Age of Terror programme, The Paris Plot - marked the GIA's most dramatic and audacious attack since its launch.
France was the enemy too, as its government supported the FLN regime. What made the hijacking historically significant was that the four jihadis who seized the plane at Algiers airport planned to crash it on Paris - seven years before 9/11.
The crisis was resolved 54 hours later, after the hijackers had shot dead three passengers in cold blood whilst the plane was still on the tarmac in Algiers.
The flight was then diverted to Marseilles where French special forces mounted a dramatic rescue operation, killing the hijackers and rescuing the passengers and crew. The rescue was broadcast on live television.
According to the French anti-terrorist judge, Jean Louis Bruguičre, the hijacking marked the beginning a new and ominous phase in Algeria's jihad.
"The GIA decided to make a strategic step in 1994, not only to fight inside Algeria which is their home ground battlefield but to export violence outside," he said.
"Algeria was only the first base for a much larger strategy to promote jihad as a tool to have a worldwide Caliphate regime in the future. The same as al-Qaeda," he added.
Rachid Ramda helped fund deadly bomb attacks on the Paris Metro
Six months later, the GIA took savage revenge making its external jihad a reality by launching a bombing campaign on the Paris Metro in June 1995.
Ten people were killed and hundreds wounded.
To the anger of the French, some of Algeria's most militant Islamists, having been refused entry to France, sought refuge in London which the French authorities now scathingly referred to as Londonistan.
They had done so well before the hijacking to escape the Algerian regime's crackdown on its enemies. The British authorities monitored the exiles' activities but did little to stop them.
In 1995, however, at the instigation of the French, British police did raid the flat of a GIA member called Rachid Ramda, who had been given asylum in Britain and whom the French accused of helping finance the Metro attacks.
And there is an interesting postscript to The Paris Plot. When British anti-terrorist officers raided Ramda's flat, they found not only a Ł5,000 money transfer to the Paris bombers but the front cover of a GIA newsletter called Al Ansar, depicting an exploding Eiffel Tower.
For 10 years the Home Office refused to agree to Ramda's extradition on the grounds that he had been incriminated in France by a former comrade whose confession was suspected to have been extracted using questionable methods.
It was only after the 7/7 bomb attacks in London that the British finally agreed to Ramda's extradition. He was sentenced to life in October 2007.
Age of Terror: The Paris Plot is on BBC Two at 9pm on 29 April