The cocaine trade first exploded in this region five years ago, as Latino cartels, faced with a saturated market in the US, sought new routes to get their product to Europe's borders. First the drug is shipped or flown across the Atlantic to lawless, corrupt coastal states like Guinea Bissau, then it is moved thousands of miles across the Sahara to Algeria, Morocco and Libya.
But while Britain and other Western nations have committed vast resources to fighting a similar narco-terror axis in the Taliban-controlled poppy fields of Afghanistan, the threat directly beneath Europe's belly has had rather less attention. The entire region has only a handful of Western counter-narcotics agents assigned to it, while many local police forces, such as in Guinea Bissau, lack even the cash to put petrol in their cars.
Now, though, the trade's potential to wreak far wider havoc has become horrifyingly clear, in helping to bankroll the al-Qaeda movements behind both the Islamist take-over of northern Mali and the murder of western workers at the Algerian gas facility earlier this month.
Among its most prominent beneficiaries is none other than Mokhtar Belmokhtar, the one-eyed jihadist and smuggler who has claimed responsibility for the mass hostage-taking in al-Qaeda's name. Nicknamed the Marlboro Man for his lucrative cigarette smuggling empire, Belmokhtar, who helped found Al-Qaeda in the Islamic Maghreb, is thought to have diversified into drugs a few years ago, earning himself the moniker of "le narco-Islamiste" on the smuggling routes between Mali and his native Algeria.
More widely, AQIM is thought to levy "taxes" on other drug smugglers in return for safe passage, earning the group a direct subsidy from the cocaine that ends up in the clubs, bars and crack dens of Britain.
Belmokhtar seems to have had no problem accommodating a sideline in "haram" contraband into his puritanical Islamic vision. As drugs are seen as a largely Western vice, jiihadists can argue that enabling them to flood into Europe is all part of a plan to weaken and corrupt the enemy.
Gao, which sits on the River Niger in Mali's north-east, has long been one of the main drug transit points, where convoys begin winding north through the mountainous dunes of the Sahara proper. Notoriously, it was the scene of the so-called "Cocaine Air" incident of 2009, when an elderly Boeing 727 airliner was found abandoned in the desert near Tarkint, a sandblown village north of the city.
The United Nations Office for Drug Control believes the plane, carrying up to 11 tonnes of the drug, had been flown direct from Venezuela - one of an entire "fleet" of decrepit airliners pressed into service by Latino cartels. The incident prompted the UNODC to warn that terror-backed trafficking in West Africa was "taking on a whole new dimension."
The hotspot of Guinea Bissau is a formidably difficult environment for trainers and counternarcotics officials to operate in, not least because, according to UN officials, many of those behind the coup and now in power have links with the drugs business.
And diplomats point out that for all the West's talk of helping to retrain Mali's chaotic army, it was already the recipient of a generous US counter-terrorism programme when it collapsed last year.
"You can spend all the money you like, but these are not easy regimes to deal with," said one serving drug enforcement officer who covers West Africa. "Some of them are already so bad that you can't achieve anything."