One can never be sure that terror offenders can be "cured" by deradicalisation programmes, according to a top British forensic psychologist, weeks after a rehabilitated terrorist hailing from Pakistan-occupied Kashmir killed two people near London Bridge.
Christopher Dean, the psychologist behind the UK's main deradicalisation programme for terror offenders, said some terror offenders who take part in his Healthy Identity Intervention (HII) scheme appear to regress because of their uniquely complex identities.
Dean spoke to the BBC after HII participant Usman Khan stabbed two people to death near the London Bridge. In the attack on November 29, he killed two people at a prisoner rehabilitation event in Fishmongers' Hall in London Bridge.
Khan, 28, was shot dead by police. His family hailed from Pakistan-occupied Kashmir (PoK).
Khan was convicted in 2012 over a plot to bomb the London Stock Exchange (LSE). He also had plans to set up a terrorist training camp on ancestral land in PoK.
He appeared to be responding to rehabilitation by the time of his release in December 2018, the report said.
The HII scheme involves the offender attending repeated sessions with a psychologist who encourages them to talk about their motivations, beliefs, identity and relationships with both other extremists and the rest of society.
The aim, Dean said, is to find ways to get the offender to think deeply about what they really want from life - and this can lead them to voluntarily abandoning extremism and violence.
Speaking to BBC Radio Four's Today programme in his first broadcast interview, Dean said the work was complex because the offenders were different to almost all others in jail.
"The two main aims of healthy identity intervention are primarily to try and make individuals less willing or prepared to commit offences on behalf of a violent extremist group cause or ideology," he said.
"If we can reduce someone's relationship or identification with a particular group, cause or ideology, that in itself may have an impact on whether they're willing to offend or not," he said.
Dean said some complex offenders he had worked with needed 20 or more sessions to show signs of positive change, because of the depth of their indoctrination.
"We see some individuals who may have been part of a group for many years or have been invested or identified with the cause for many years. (Leaving that group) is an incredibly difficult thing to do," he said.
Dean said the HII sessions were only one part of attempts to manage such offenders - and the results of the prison scheme should be clearly understood by the probation and police officers monitoring someone after their release.
"They may come into contact with individuals or they may go through a spell in life where they may begin to re-engage with groups or causes or ideologies associated with their offending behaviour.
"I think we have to be very careful about ever saying that somebody no longer presents a risk of committing an offence. I don't think you can ever be sure. We have to be very careful about saying someone has totally changed or has been cured."
The inquests into the deaths of Khan's victims are likely to hear evidence about how the killer was managed in prison and in the community after his release, the report said.
The UK's Ministry of Justice has not completed any work to test whether the HII scheme prevents reoffending or successfully tackles extremist behaviour - and there has been no similar exercise to test the effectiveness of the follow-on programme Khan joined after his release on licence.
However, Dean said that when he and colleagues devised HII it was not rolled out until an external panel of experts assessed whether it was clearly based on the best-available evidence about challenging extremist mindsets.
HII could not currently be tested like other rehabilitation programmes, he said, because there were too few offenders to get a scientifically-robust assessment of what worked.
British prime minister Boris Johnson has said the "grim reality" is that "some people can't be rehabilitated" in prison.
He has also called for longer sentences and an end to automatic release of convicted prisoners after the incident involving Khan in November.
Johnson has revealed that 74 people jailed for terror offences and released early in the UK will have their licence conditions reviewed.
The Ministry of Justice launched the urgent review after the London Bridge incident involving Khan, who had served half of his sentence, killed two people.
Damian Talbot