Today it is taken for granted that governments will co-operate in the fight against the heroin and cocaine trade.
But 100 years ago, narcotics passed from country to country with minimal interference from the authorities. That all changed with the 1912 International Opium Convention, which committed countries to stopping the trade in opium, morphine and cocaine.
Then, as now, the US stood in the vanguard against narcotics. While the UK's position is unequivocal today, a century ago it was an unenthusiastic signatory, says Mike Jay, author of Emperors of Dreams: Drugs in the Nineteenth Century.