According to the UN 93% of the world's opium is grown in Afghanistan.
(According to their annual report, in 2009, opium cultivation in Afghanistan decreased by 22%, from 157,000 hectares(ha)in 2008 to 123,000 ha. The whole of the UK is 24 million hectares. With 93% of production coming from one country I'm surprised the monopolies commission hasn't got involved.)