Three people, including two from Clapham, have pleaded guilty to the charges against them.
Another person was found guilty at Kingston Crown Court.
Batches of MDMA were being shipped to areas across South London.
The four will be sentenced on June the 7th.
Detective Inspector Lydia Stephens of the Metropolitan Police Specialist Crime Command said,
“These individuals were heavily involved in the large-scale supply of Class A drugs in London that severely impacts our communities, drives violence and can lead to vulnerable people and children being criminally exploited across the city.
“Apprehending them successfully is the result of months of hard work and dedication on the part of a team of highly skilled Met detectives, supported by colleagues from the National Crime Agency and Border Force.
“We are committed to bringing organised crime groups to justice and making London safer.”
