From the Black Hawk the immaculate rainforest is broken by pockets of coca fields. Planes fly beneath spraying the coca. Photographer: David Notman-Watt
Every year the US pours money into the Colombian military as part of a controversial coca eradication plan, Plan Colombia.
Alex James talks to an informer who leads commandos to a cocaine factory in the rainforest.
A coca farmer explains: "We don't grow it because we want to. We grow it because we have no choice. Without it we can't survive."
There are hundreds of makeshift cocaine labs in the rainforest. Here coca leaves are turned into cocaine base.
First the leaves are ground and mixed with cement, then petrol is added. This releases an alkaloid in the leaf.
Cold water and sulphuric acid are added, then the petrol is drained to leave a paste which is boiled and mixed with another chemical.
The resulting paste is called "pasta basica". It will now be sold on to bigger labs for processing into cocaine hydrochloride.
A barrel of leaves makes about 50g of pasta basica. This makes 25g of pure cocaine that will be worth about £3,000 in London.
In Modelo prison there are 250 foreigners. Steve, a prisoner, explained: "The money's just too good... All of the Spaniards in my patio, 99% are mules and they're all here for cocaine."
The grave of Pablo Escobar, or "El Patron", the head of the Medellín drug cartel. He was shot as he tried to flee security forces in 1993.