The Streatham attacker wasn’t born a terrorist, he was made into one – early release is far from the problem

The case for longer detention is fundamentally weak. If anything, the London terror attack shows how easily and rapidly very young minds can be moulded by contact with certain material

Sudesh Amman, the man responsible for stabbing two people in Streatham on Sunday, had been released from prison about a week before. He had served about half of a sentence for terror offences. The question of his automatic “early” release (it is a long-standing convention), therefore, has understandably been raised.

The suggestion is that if Amman had still been in a cell somewhere on Sunday afternoon, rather than roaming around south London, he would obviously not have been in a position to try to mount any kind of terror attack. Therefore, the argument runs, no one should be released earlier than their nominal tariff.

The prime minister’s response was typical enough when he declared: "I’ve come to the end of my patience with early release."

It is for that reason – and, of course, that the natural inclination among panicky politicians is to be seen to “do something” to assuage public anxiety and appease a mostly alarmist press – that the government has proposed to stop terror suspects from being released without Parole Board assessments.

The justice secretary, Robert Buckland, argues that ending automatic releases would allow the authorities to keep those who pose a danger to the public under lock and key in “an unprecedented situation of severe gravity”. The proposal has already met with opposition and the perfectly valid objection that sentences cannot be altered retrospectively, emergency or not.

The more pressing flaw in the government’s idea, even for those relaxed about ancient civil liberties, is that it wouldn’t actually work very well. We know from harsh experience that, with some terror suspects, detaining them for a longer time will merely postpone the problem.

Some of those already radicalised and resistant to being de-radicalised in prison will retain their deadly intent for however long it takes them to exercise it – months, years, perhaps even decades. Others will become more firmly indoctrinated.

It is obvious that Britain’s prisons are, to put it mildly, under pressure. The worst prisons are unsafe for those who find themselves inside – staff, visitors and the inmates themselves. Ridden with drugs such as spice, and with violence commonplace, they have doubled up for too long as universities of crime and, nowadays, colleges for radicalisation and terrorism.

The longer prisoners are allowed to fester there, the more chance that their Islamist – and other extremist – prejudices will be incubated into something even more deadly. And those who are capable of reform and rehabilitation (and there are examples working to keep the peace today) will find it harder to turn their lives around under indiscriminate heavier sentencing.

According to Amman’s mother, the time he spent in Belmarsh prison did deepen his beliefs. However, the process had begun before then and he was plainly radicalised online as an even younger man – he was, after all, still only 20 when he was shot dead.

What the Streatham terror attack more clearly shows is just how easily and rapidly very young minds can be moulded merely by contact with material on the internet. It is foolish to imagine that Isis and other propaganda machines can ever be effectively closed down – the web is simply not amenable to such policing.

However, via the intelligence agencies and police work, the authorities are able to monitor the worst excesses and the heaviest consumers of such materials. That at least would be a starting point for trying to stem the tide of hate. So would ever more engagement in communities. Nor, it bears repeating, is the proliferation of violent propaganda confined to one group – far right groups are also avid users of the internet, social media channels and private networks to further their aims.

If Amman, in other words, had been less exposed to these doctrines, he might not have wound up in Belmarsh in the first place and subsequently tried to kill his fellow citizens. Terrorists are not born, but made.

The case for longer detention as the necessary and sufficient condition to suppress terror is, therefore, fundamentally weak. It does, however, leave society with the awkward question as to what to do about those who plainly have an evil intention, with a range of evidence to back that suspicion known to the authorities, but who have not yet found the opportunity to carry out an attack. They may be in jail, awaiting release, or not. Either way they represent a threat, but one short of the point at which they can be prosecuted and placed in custody. These are the most difficult cases of all.

There is a parallel, albeit imperfect, with the detention that is permitted for certain mental health conditions – “sectioning” – and, indeed, there can be some overlap between the two.

In 2017, for example, Adrian Brown, a man with schizophrenia​ who was suffering a psychotic episode, boarded a London Overground train at Honor Oak Park station (about five miles from Streatham). On board, he found Muhammed Ali and stabbed him six times, causing severe blood loss and a punctured lung. He wandered the train shouting: “I want to kill all Muslims.” Could he have been indefinitely detained before he tried to kill an innocent man because of his mental condition? Or because of his terrorist tendencies? Or both?

Perhaps too little has been made of the rapid police response to the Amman attack. Although Amman was able to move about, he was plainly under active and close supervision by the Met and was stopped before he could do any more damage. The police did their job right.

Yet until some legally defensible system of suspending habeas corpus for those who are still technically sane can be devised, the problem of controlling terror and terrorists (in jail or not) will remain one of restraint, surveillance and intelligence.

In fact, a regime of exceptional indeterminate sentencing was introduced by the last Labour government in 2005 – Imprisonment for Public Protection for adults and Detention for Public Protection for minors.

These were, abolished in effect by the Conservative-led coalition government in 2012, and they do not seem to be back on the agenda even now. So the criminal justice system and the hard pressed intelligence, police and probation services are left with tagging as one alternative, as well as injunctions on movement, association and snooping on internet use and telecoms.

It is as well to acknowledge that such measures can never be 100 per cent effective, any more than simply doubling the amount of time terrorists spend in jail would be.