Police say they are finally turning the tide on drug dealers selling on the darknet – a secretive part of the internet which has been described as like “online shopping for drugs.”

The UK’s National Crime Agency says recent international takedowns of so called dark markets and arrests in multiple countries are a result of new techniques in cyber policing that is giving them the upper hand.

However, BBC research suggests that police around the world have an uphill struggle on their hands as many dealers - known as vendors - have survived multiple market place collapses by operating across many different darknet sites.

The BBC’s cyber reporter Joe Tidy and BBC data journalist Alison Benjamin journey into this hidden world to speak to vendors and buyers and uncover secrets of the trade

The programme reveals the major role played by UK dealers in the global business which is estimated to be worth more than a billion dollars a year.

Reporter: Joe Tidy

Producer: Paul Grant

Editor: Maggie Latham