But with the demise of the Taleban, there are fears Afghanistan will quickly reclaim its status as the world's largest producer of illicit opium.

The UNDCP provides estimates of the level of opium poppy cultivation per region by conducting a census of farmers on the ground.

Opium cultivation and processing is most extensive in the south of the country, in particular Helmand province.

Laboratories convert the raw opium into a morphine base, white heroin or one of three grades of brown heroin.

This is then transported through a number of intermediate countries - where it is sometimes further refined and processed - before being shipped on to Europe and North America.

Makeshift factories synthesise the heroin from opium sap

In the past, a large number of laboratories were located across the border in Pakistan's tribal region, but a Pakistani Government crackdown has forced many of these to relocate across the border.

Afghanistan also produces a large amount of hashish - a processed form of cannabis - which is mainly transported through Pakistan and the Central Asian republics.