"High risk" and dangerous far-right extremists in Wales have been prevented from carrying out violent attacks in the last three years, according to a Home Office advisor.
A Newport man was preparing for a "race war" by making and testing explosives.
Nick Daines, who works with the UK Government's counter-terrorism Prevent programme, said Wales has a "unique landscape" for far right extremism.
But he said membership was still relatively small.
Welsh counter terror police said they devoted as much time to far-right extremism in Wales as Islamist extremism.
Nigel Bromage, co-founder of the violent neo-Nazi group Combat 18, said Wales had traditionally been seen as a "safe haven" for the ultra-right, away from the authorities.
He now works to confront the far-right through his organisation, Small Steps.
He said groups like the National Front had tried to hijack causes like the miners strike in the 1980s to help spread their ideology.
"South Wales was seen as a big area to not only go in and support the miners, offering food and picket line support, but it was also very much about once we were in that community we could open up and support other things," he said.
Mr Bromage said the groups would not initially advocate violence, or Nazism as they knew people in Wales would reject that.
He said the tactics were a "slow burn", and he believes the same tactics are being used by the far-right in Wales today.
His organisation is now beginning to hold sessions in Wales to educate people on the dangers of the far-right.
Just over 7,600 people in England and Wales were referred to the UK government's Prevent programme in 2015-16 - about 5,000 them over concerns about Islamist extremism.
According to the Home Office figures - Wales accounted for just 2% of those referrals - 148 cases.
But of those Welsh cases - 22% were for concerns about far-right extremism.
Officers from The Welsh Extremism and Counter Terrorism Unit said they investigate every Prevent referral carefully.
Experts believe the high proportion of far-right referrals is a genuine reflection of what is being seen in Wales, and not a consequence of the low number of overall referrals.
Nick Daines, a Home Office Prevent co-ordinator, works across Wales with people who are in danger of - or have become radicalised.
He has 20 cases ongoing, and rarely speaks about his work.
Much of his role involves providing support and guidance in matters that could be completely unrelated to extremism, such as employment, housing or education.
He said isolated parts of the South Wales valleys remained "strongholds" for the far-right, contributing to Wales' "unique" far-right landscape.
He said the mindset of the people he works with was becoming more extreme.
"There are significant problems along the M4 corridor from Newport across to the furthest parts of West Wales," he said.
'Race war' preparations
"I worked with a man in the Newport area that was acquiring operational manuals for paramilitary groups and was creating explosives and experimenting with those in a quarry.
"He was very racially motivated and held a perception there was a coming race war and needed to prepare for that kind of eventuality."
Mr Daines said there had "certainly has been" moments where he had helped stop violent acts being carried out in Wales.
He believes one "high risk" individual from south Wales who had a "propensity for violence" would have "acted on his views" - had the authorities not intervened.
He said incidents where people prepare explosives or weaponry are "not as rare as you would think".
But he said the membership of far-right groups is still relatively small in Wales and that the public should not be worried or alarmed.
Senior officers at The Welsh Extremism and Counter Terrorism Unit said they had particular concerns about one emerging group, called the System Resistance Network.
Their posters were found in a student area of Cardiff this month - officers believe they are trying to attract young people.
Experts on the far-right claim former members of the now banned group Nation Action have switched to the System Resistance Network.
Their social media posts display Nazi iconography.
The System Resistance Network is not a banned group.
Zach Davies, who was convicted of attempted murder after attacking a dentist in a supermarket in Mold, claimed links to National Action.
Senior Officers at The Welsh Extremism and Counter Terrorism Unit said half their time was devoted to combating far right extremism, as much as Islamist extremism.
Officers said the threat had never gone away, and urged people to contact them if they suspected someone was being radicalised.
Assistant Chief Constable Jon Drake from South Wales Police said the Prevent programme can help stop someone committing potentially criminal acts.
"This is often work a long long way before there's any criminal offending, it could just be someone needing some advice some guidance, the clue is in the title - the prevention of harm".