“It’s my mission,” says a member of a Leeds-based group called Predator Hunter as they drive the streets in a white van looking for a person they suspect of being a paedophile. “I'm going to catch this man and I will get him tonight."
Predator Exposure is among a rising number of amateur groups that seek to hunt down and expose online paedophiles. The group describe themselves as a "new breed of hunter" that aims to expose suspected predators live online and whose members carry radios and wear police-style high-visibility vests.
But the man in the van, a mixed martial arts fighter, insists they are not "vigilantes".
"Vigilantes will go smash windows and chuck petrol bombs," he says. "As soon as we make contact, we get on the blower and phone the police and we do safeguarding to make sure he's safe."
However, they are one of the groups that are the focus of Paedophile Hunters: The Rise of the Vigilantes - a new BBC Three programme that lifts the lid on a growing issue of people tracking down and confronting online predators in the UK.
Video appears to show one man shouting "die, die" at one suspect who has been bundled to the ground and warns the hunters he is about to faint.
On the programme, the group can be seen stopping another man they have accused of trying to speak to a one of their decoys. As thousands watch a live stream of the confrontation, a man from a nearby pub becomes aggressive and has to be held back. Viewers are told the man targeted by the hunters was later given a suspended jail sentence.
But despite convictions like this, such groups are at the centre of considerable controversy.
Across the UK, there are believed to be around 75 of these groups with names such as Guardians of the North, Dark Justice and Plymouth Against Paedophiles.
Supporters believe they are helping over-stretched police forces catch abusers, with a BBC investigation last year finding that their evidence was used to charge suspects at least 150 times in 2017.
But critics, who include senior police officers, warn the vigilante groups could harm legitimate police investigations and risk breaking the law while "entrapping" and confronting suspects.
The figures are certainly startling. In recent years there has been a dramatic surge in the number of online child sex abuse images uncovered in the UK, with the National Crime Agency saying last year it had received more than 82,000 referrals of child sex abuse images in 2017 - up 700 percent from 2012.
At least 80,000 people are estimated to pose a sexual threat to children online - and a rising number are believed to be taking advantage of technology such as the dark web and encryption to evade detection.
But the net is closing, with more than 130 suspects including an ex-police officer, a children's entertainer and five teachers, arrested one week-long crackdown by the agency and police forces, leading to 165 children being saved from harm.
As part of the programme, journalist Livvy Haydock met members of Guardians of the North, which was set up in 2016 and whose leader says its work is aimed at protecting children.
"It's an epidemic," the man tells the programme. "It's thousands every single day trying to prey on our children. It's a dark world. People out there lead normal lives until 5pm and change into a different person and become a predator online."
The methods used by the groups such as Guardians of the North to track down suspects are exposed in the programme - with "decoys" deployed online to pose as underage children and wait to be contacted by adults.
One decoy's phone continuously beeps as she receives an apparently constant stream of messages. "That's another pervert trying to talk to a kid," she says. Another adult woman decoy tells how she is regularly moved to tears by the horrific messages and images she receives.
Suspects identified as trying to groom young people are then tracked down - the confrontation often streamed live on social media as the police are called. And it is here where the groups are felt by police officers to cross a further line - in addition to the risk of handling indecent images.
In June 2017, two men were charged with affray after they attacked a man while he was being confronted by hunters in Kent.
In February last year, an inquest was told a man took his own life after being confronted by the Southampton Trap group when he allegedly arranged to meet a 14-year-old boy in a supermarket car park.
Earlier this month, it was reported that national police chiefs had ordered local forces to crackdown hard on the vigilante groups - even telling officers to pursue them with the full force of the law.
According to internal guidance seen by the Times, forces have been told to investigate potential harassment, privacy and violence offences as vigilante groups have "little or no consideration" for the safeguarding requirement of victims of the paedophiles they have outed.
But while the debate about the paedophile hunters continues, are they here to stay?
"If you saw someone robbing a bank and you had an opportunity to make a citizen's arrest, you would do it," rationalises one member of Guardians of the North in an interview with Haydock. "We have that opportunity and we're taking it."
"Will you ever stop?" Haydock asks. Without a pause, he has the answer: "Why would I stop protecting children?"
Paedophile Hunters: The Rise of the Vigilantes will be available on BBC Three from Sunday 27 January.