- At least 20 people were placed under investigation globally last year following the BBC's investigation.
- Three participants have already been charged in the US, including the ringleader of the group, Macartney.
A British woman has pleaded guilty to being part of a global monkey torture network.
Holly LeGresley, 37, from Kidderminster, was a participant in a private online group that was paying people in Indonesia to kill and torture baby monkeys on video.
The convictions follow a year-long investigation by the BBC Eye team.
They went undercover in the groups to expose the existence of the sadistic global network.
Warning - this story contains distressing content
LeGresley pleaded guilty at Worcester Magistrates' Court on Tuesday to charges of consuming, causing and facilitating the torture of baby monkeys over the internet.
The prosecution said LeGresley showed a desire to harm vulnerable creatures and that she also had a hatred towards pregnant women and children.
The 37-year-old was part of a group on the messaging app Telegram that brainstormed, crowdfunded and then commissioned videos of monkeys being tortured by people in Indonesia.
The group was used to share ideas for custom-made torture videos such as setting live monkeys on fire, injuring them with tools and even putting one in a blender.
The ideas were then sent, along with payments, to video-makers in Indonesia who carried them out, sometimes killing the baby long-tailed macaque monkeys in the process.
Under the username "The Immolator" LeGresley once ran a poll for members of the group on which method of torture should be inflicted upon an infant monkey.
LeGresley will be sentenced at crown court on 7 June.
BBC Eye identified her as a participant in a group run by a US man called Mike Macartney, a former motorcycle gang member who served time in prison and went by the screen name "Torture King".
LeGresley, who at the time was living with her parents in the Midlands, was among the most active participants in the group and was made a group moderator by Macartney.
She would often message privately with Macartney, who pleaded guilty this month to animal abuse charges in the US and is facing up to five years in prison.
Kevin Lacks-Kelly, the head of the UK National Wildlife Crime Unit, said LeGresley played a key and active role in the global torture network.
He said she was much more than a spectator, that she raised funds, archived videos to share between groups and acted as an admin in the groups welcoming new members.
"I've been investigating wild crime for 22 years and it sickens me to say that this is unequivocally the worst case I have ever investigated or overseen," he said.
Sarah Kite, a co-founder of the animal charity Action for Primates who investigated the groups, said LeGresley "unquestionably derived enjoyment from watching helpless infant monkeys in terror and pain fighting for their lives".
"The depth of the depravity and perversion... in facilitating the horrific and gratuitous torture and killing of vulnerable baby monkeys was sickening, something I had never seen previously," she said.
Another woman, Adriana Orme, 55, from Upton-upon-Severn, also appeared at the magistrates' court on Tuesday in connection with the network.
She chose not to enter a plea at this stage to charges of publishing an obscene article and for causing unnecessary suffering to a protected animal.
Her next appearance in court will be on 5 June.
At least 20 people were placed under investigation globally last year following the BBC's investigation.
Three participants have already been charged in the US, including the ringleader of the group, Macartney.
David Christopher Noble, 48, a former US Air Force officer who was previously court-martialed and dismissed from the military, and Nicole Devilbiss, 35, faced the same charges as Macartney and are both facing up to five years in prison.
Along with Macartney, the BBC identified two other ringleaders in the monkey torture network - Stacey Storey, a grandmother in her 40s from Alabama who was known in the community as "Sadistic", and a man known as "Mr Ape", whose real identity we cannot reveal for safety reasons.
Both were expected to face charges for their role in the groups.
Police in Indonesia also arrested two torture suspects.
Asep Yadi Nurul Hikmah was charged with animal torture and the sale of a protected species and sentenced to three years in prison.
M Ajis Rasjana was sentenced to eight months - the maximum sentence available for torturing an animal.