How do you untwist some of Britain's most warped minds?
It is a question without a simple answer, but one that is only being asked more often.
The number of terrorist offenders across the UK's prison estate is rising. There are now around 200 in total, from those who've plotted attacks to those who've committed mass murder.
They aren't just Islamist extremists, a quarter are inspired by the far right. And those who have any prospect of being released must be reformed, or they risk reoffending.
But in recent years the ability of our prison service to successfully do that has been called into question.
All terrorists are asked to take part in deradicalisation programmes in jail, with one-to-one mentoring, psychological and religious guidance on offer to try and change their world view.
Only a small percentage of terrorists released go on to reoffend, but when they do it is often with deadly consequence.
Usman Khan claimed to have deradicalised before he killed two at Fishmonger's Hall in London Bridge in 2019. Sudesh Amman had also gone through deradicalisation programmes before he went on a stabbing spree in Streatham last year.
With those cases in mind, we were offered exclusive access to two of Britain's highest security prisons, where many of the most dangerous terrorists are housed.
We spoke to psychologists and imams who work closely with them.
So, how do you incentivise a terrorist to change their ways? To give up the status that their crimes afford them within their own extremist niche?
What alternative life can you offer them? A new job and a happy place in society? Unlikely.
When their crimes have cost lives and their own liberty, how do you persuade them to drop the meaning they've attached to what they've done and face the cold hard truth that most are simply just murderers?
In a frank admission, the Justice Secretary told me it simply isn't always possible to do any of those things. "Do you believe some terrorists are beyond reform?" I asked him.
"Yes," he replied bluntly.
'This is difficult work': Robert Buckland tells ITV News the system must do its best to work out genuinely reformed terrorists
So, instead, since 2017 a new approach has been used in certain cases. Moving the most radical minds to Separation Centres - prisons within prisons - where they are kept away from other inmates they may try to recruit to their cause.
We gained the first ever access to one of these centres at HMP Frankland in Durham, where terrorists have their own separate exercise yard and sleeping quarters.
There, we observed a man we believe to be the Manchester Arena bomb plotter Hashem Abedi socialising with another inmate we've identified as a former Taliban fighter also jailed for terrorism offences.
And herein lies the dilemma. If you separate, do you also elevate? Do you afford extra status to terrorists who still believe they are carrying out god's work?
Behind cell doors, we could hear the inmates at Frankland referring to the Separation Centre as their "paradise" - as if their placement there was some kind of divine intention.
The Justice Secretary admits that this is a problem. But regardless, he told me he has decided to review the use of Separation Centres to make it easier to place terrorists inside them.
Robert Buckland confirms the government is reviewing how to increase the number of terrorists in separation cells
Currently, there are 28 cells available across the country in such centres, but we understand only around a third of them are full.
Robert Buckland says he wants to change that. "I’m committed to reviewing the process to make sure it is as streamlined and as straightforward as possible with the clearest rationale.”
In other words, there is too much bureaucracy involved in moving terrorists to these centres. It could be simplified.
But the more terrorists you move, the bigger and more concentrated the pool of extremism you could create. More and more could end up being beyond all reform.
In Frankland, only one out of five terrorists in the separation centre is even entertaining any prospect of deradicalisation.
There is no easy way - not even for the imams and other religious leaders - to persuade terrorists to abandon what they believe to be their criminal calling.