Some of the leaders of self-styled paedophile-hunting groups operating in Northern Ireland have been identified for the first time.
There are increasing concerns about the methods many of the groups use, and their lack of accountability.
The so-called paedophile-hunting groups target people online who they believe are sexual predators.
They confront them and broadcast the encounter live on the internet, then call the police.
There have been more than 100 incidents of that nature reported to police in Northern Ireland, but no-one has been charged as a result and there have been no convictions.