The contrast could not have been sharper. David Merritt, the father of the first named victim of the London Bridge terrorist, responded: “My son, Jack, who was killed in this attack, would not wish his death to be used as the pretext for more draconian sentences or detaining people unnecessarily.”

But he had barely uttered the words before Boris Johnson was vowing to introduce a “tougher” sentencing regime that would, in the words of the headline writers, “lock terrorists up and throw away the key”.

The prime minister’s unseemly rush to avert a repeat of the politically damaging debate about police numbers in the aftermath of the previous London Bridge attack, in the middle of the 2017 general election campaign, has led him to ask the wrong question.

Jack Merritt: London Bridge attack victim described as 'best guy' Read more

In his tortuous attempt to find a way to blame Labour for the attack, Johnson wants us to relentlessly focus on the question of how Usman Khan could have been let out so early. The real question to be asked is, how could a convicted terrorist spend eight years inside the English prison system and still emerge a radical jihadist?

The answer has to be viewed against a background of prison and probation services that have faced part-privatisation and cuts, under austerity, of 40% in funding during the time that Khan was in prison. Prisons have had to cope with record levels of violence, assaults and suicides.

As the former chief inspector of prisons, Nick Hardwick, put it on Sunday: “Let’s be clear. All this talk about longer sentences, deradicalisation programmes and closer probation supervision – who, precisely, is going to do this? These are services in crisis, haemorrhaging experienced staff and struggling with chaotic reforms.”

Official concern about slow progress in turning prisoners away from terrorism and concern about their release into the community emerged as long ago as 2011.

A Home Office review of the Prevent counter-terrorism strategy revealed that there was “no proven methodology” and the bespoke programmes that had been developed had “only reached a small proportion of the target population and have not kept pace” with the increasing number of releases of terrorist prisoners.

However long convicted terrorists are locked up, with the exception of a limited number, they are all going to have to be released eventually

Two main intervention programmes have been developed since 2007 to tackle the problem. Healthy Identity Intervention delivers one-to-one individually tailored sessions, and al-Furqan (meaning distinguishing truth and falsehood) is specifically for Islamist offenders whose ideology has become bedded in extremist interpretations of Islam. Both were regarded by the peer-reviewed Prison Service Journal as still in their “relative infancy” in 2012.

Those convicted of terrorism-related offences who are released into the community are managed under multi-agency public protection arrangements used for convicted sex offenders with a battery of extra restrictions, including denial of access to the internet. It is a challenging system for a part-privatised probation service in crisis. Khan is said to have complied with all his restrictions in the 11 months since his release.

Michael Gove did try to address this lack of progress in prison deradicalisation programmes when he became justice secretary in 2015. His somewhat obsessive interest in Islamist radicalism had led him to write a book, Celsius 7/7, and commission a report from a former prison governor and Whitehall official, Ian Acheson.

Acheson wrote in the Sunday Times that there were 220 people like Khan currently in the system but there had been“little tangible progress” since his report. He accused the prison and probation service of “institutional timidity” and lacking the “leadership, competence or will” to deal with the terrorist threat.

As a recent Ministry of Justice (MoJ) analysis report revealed, enormous effort went into implementing Gove/Acheson’s principal recommendation, which was to set up a network of high-security separation centres – quickly dubbed “jihadi jails” – to remove the hardest cases from the mainstream prison population and to tackle their radicalisation.

The 2019 MoJ research also revealed that only two of the three funded separation units had opened in high-security jails because of a lack of referrals, and that each had held only three to six men at any one time. The third unit has still not opened. More worryingly, the MoJ study also concluded that a key challenge was that many of the men had “refused to engage in aspects of the centres, especially interventions to support disengagement from extremism and address their offending behaviour”.

Boris Johnson blames Labour for release of London Bridge killer Read more

Other criminologists have reported that there is a widespread refusal among extremist prisoners to take part in deradicalisation programmes. It would seem that reports that Khan’s unsuccessful request to participate were the exception rather than the rule. Gove needs to account for why, after so much effort, his flagship “jihadi jails” have so far failed.

With reports that as many as three-quarters of convicted terrorist prisoners reject engagement with the deradicalisation programme, this must be the fundamental issue to be tackled.

Against this background Johnson’s obsessive focus on ending all automatic early release is not only dangerously misplaced but also ignores the fact that there is no such thing as “automatic early release” now for prisoners convicted of terrorism-related offences. However long convicted terrorists are locked up, with the exception of a limited number of the most heinous cases, they are all going to have to be released eventually. The “lock ’em up and throw away the key” battle cry may suit a panicked politician in the middle of a general election campaign, but it isn’t going to keep us safe from another Usman Khan.

• Alan Travis is the former Guardian’s home affairs editor