What does it take these days for a nihilistic terrorist to get locked up in prison for the rest of his life?

In America, that's a relatively simple question: if you're a convicted Al-Qaeda or ISIS operative, you're led to a small cold foreboding window-less cell and you don't come out again.

Ever.

Well not back into society, anyway.

That's your punishment for deciding to align yourself with the worst terror groups in modern history - responsible for mass murder and carnage on a grotesque, heinous scale.

Americans take the view that if you're part of an organization that beheads aid workers, throws gay people off roofs, sets victims on fire in cages, or flies planes in to sky-scrapers, then you're unlikely to rehabilitate to an extent where you can be trusted not to carry on doing such diabolical things.

But in Britain, we take a rather different approach.

If you're a convicted Al-Qaeda terrorist in my country, then you get to walk free after just eight years, without anyone even bothering to check if you're still dangerous.

Sounds insane, right?

Well that's because it IS insane.

Usman Khan, circled, is pictured with terrorists Mohibur Raham, Gurukanth Desai, Abdul Miah , Mohammed Chowdhury, Mohammed Shahjahan in Roath Park in July 2010. He carried out the brutal attack on London Bridge on Friday that left two people dead and three others injured

Two heroes, one armed with a whale tusk and another with a fire extinguisher, try to prevent Khan from carrying out more stabbings. At the time, Khan (far left) was wearing a fake suicide vest

Khan's horrifying attack came less than a year after the terrorist was released from prison. And by cruel irony, his victims were trying to help ex-prisoners like him at a rehabilitation conference when he mercilessly stabbed them to death

And to illustrate just how insane it is, the Al-Qaeda terrorist I am referring to committed an appalling act of terror in London last Friday, murdering two brilliant young Cambridge-educated people in their 20s, and wounding three others, during a violent rampage that only ended when heroic members of the public stopped him with a fire extinguisher, whale tusk and their fists before police arrived to shoot him dead.

The horrifying attack came less than a year after the terrorist was released.

And by cruel irony, his victims were trying to help ex-prisoners like him at a rehabilitation conference when he mercilessly stabbed them to death.

The murderer was a man named Usman Khan.

And it's worth examining exactly who he was and what he did prior to his deadly attack.

Khan was a British-born son of Pakistani immigrants.

When he was just 14, he used to walk around his school, Haywood High in Stoke-on-Trent with a photo of Osama Bin Laden attached to the front of his exercise book, and he was spotted laughing at videos of the 9/11 attacks in a café.

Later, he began preaching Islamic extremism on the streets, on behalf of infamous hate preacher Anjem Choudary's banned terror group al-Muhajiroun.

Khan, who called himself Abu Saif, was photographed waving an Al Qaeda flag as he ranted into a megaphone.

He distributed disturbing extremist literature until it attracted the attention of anti-terror cops who raided his family's home when he was 17.

'I ain't no terrorist,' he insisted.

And the Crown Prosecution Service decided not to press criminal charges due to lack of hard evidence that he was.

An emboldened Khan vowed: 'We are going to carry on until the last breath, because we believe this to be true.'

He spoke at a conference about why Britain should adopt Sharia law and campaigned to stage a march through a military town where British soldiers who died in Iraq and Afghanistan were honored.

Khan became a member of Islam4UK, another of Choudary's banned extremist groups, which led to security services launching a second covert surveillance operation against him in 2010.

And that's when his real nefarious intent was uncovered.

Bugs installed in his home recorded Khan talking how to make a pipe bomb after seeing a 'recipe' in an Al Qaeda magazine. He was heard calling non-Muslims 'dogs' - and talking about buying weapons and attacking pubs and clubs with explosives.

He and two other jihadists from Stoke made contact with other extremists in London and Wales, and the nine of them met up to discuss how to train terrorists in a camp, embark on letter-bomb campaigns, blow up civilians, and attack targets including London's Stock Exchange, the US embassy in London and Britain's new Prime Minister Boris Johnson.

Saskia Jones, 23, of Stratford-upon-Avon, died alongside Jack Merritt, 25, of Cottenham, Cambridgeshire, after Usman Khan went on a stabbing frenzy in London on Friday

Jack Merrit was also killed in the attack. He studied law at Manchester University before doing an postgraduate degree at Cambridge

When they were arrested, Khan pled guilty to planning a terror camp, advised he would get a reduction in sentence by doing so.

At his trial, the judge singled Khan out from the others.

Justice Wilkie, sentencing him to just 16 years in prison, wrote that Khan's 'ability to act on a strategic level' and to plan terror attacks meant he should only be released if and when a parole board was convinced he was no longer a threat.

Wilkie warned that the nine jihadis, including Khan, 'would remain, even after a lengthy term of imprisonment, of such a significant risk that the public could not be adequately protected by their being managed on license in the community.'

Yet just eight years later, Khan was released on license into the community.

How the hell did this happen?

It started when the cunning terrorist began playing the deradicalized card immediately he was imprisoned.

'I don't carry the views before my arrest,' he said, 'and can prove at the time I was immature, and now want to live my life as a good Muslim and a good citizen of Britain.'

His strategy worked, and a year later, three Appeal Court judges led by Sir Brian Leveson inexplicably concluded it was wrong for him to have received such a 'tough' indeterminate sentence and gave him a determinate one instead that meant he would automatically be released after eight years.

So, last December, Khan was let out of prison without any formal assessment of his potential risk.

He was just electronically tagged and ordered to report twice weekly to a parole officer.

He was able to hoodwink everyone into believing he was a changed man, even joining Learning Together, a program run by Cambridge University, that rehabilitates prisoners.

And it was at their conference on Friday that he carried out his barbaric attack.

Khan distributed disturbing extremist literature until it attracted the attention of anti-terror cops who raided his family's home when he was 17 but claimed he had been deradicalized after he was jailed in 2010

Khan was shot dead by police on London Bridge shortly after carrying out the attack on London Bridge on Friday

Khan had been given a day-release to attend the event without any escort.

His victims, Jack Merritt, 25, and Saskia Jones, 23, were two young people working with the ex-cons that day who cared passionately about criminal justice.

'Jack was an intelligent, thoughtful and empathetic person (who) lived by his principles,' said his family.

'Saskia was a funny, kind, positive influence... and was generous to the point of always wanting to see the best in all people,' said her family.

My heart breaks for them both and their poor families.

I can't imagine anything worse than losing a child in such disgusting circumstances.

Although actually, I can.

Imagine hearing your child had been stabbed to death by a convicted Al Qaeda terrorist who'd served just eight years in prison and not even seen a parole board before his release to properly assess his current danger levels?

The British justice system is a hot, shameful mess.

The prisons are over-crowded and woefully under-staffed.

The probation service is also creaking at the seams and totally incapable of keeping up with all the serious criminals they are charged with keeping an eye on.

Police numbers have been drastically and disastrously slashed in recent years.

And supine politicians who predictably raced to score cheap, petty and utterly insensitive points against each other after Friday's attack, have all conspired to substantially reduce our capacity to defend the country from murderous jihadists.

As I write this column, there are 73 other convicted terrorists who've been released early back onto the streets of Britain. One of them was re-arrested after the London Bridge attack because police found new evidence he may be planning a terror attack.

Another 400 battle-scarred Al Qaeda and ISIS fighters have returned from war zones like Iraq and Syria to also freely roam around.

And police estimate there may be a further 20,000 jihadists in Britain, brainwashed and radicalized.

Who are they?

Where are they?

What danger do they pose?

The most shocking and disturbing thing about those questions is that the authorities don't seem to really know.

What we do know is that releasing Usman Khan after just eight years proved to be a bloody fiasco.

And it was always going to be a bloody fiasco.

As Nigel Farage, leader of the Brexit Party, said: 'Nobody apologizes for the fact the liberal elite have given us a ridiculous sentencing system. I don't care if you were in prison for six years or 12 years, if you have committed mass murder or planned to commit mass murder, you are not just an ordinary criminal, you have got the virus of jihadism. I don't think these people should ever be let out of prison unless we are absolutely convinced they do not have a jihadi virus. But political correctness stops us doing that.'

I agree with him.

It's not like we don't already do this for some violent offenders.

There are currently 74 prisoners in Britain who've been given 'whole life' sentences, meaning they will never come out.

They include serial killers like Peter 'Yorkshire Ripper' Sutcliffe, murderous pedophiles, and a far-right fanatic named Thomas Mair who assassinated female Member of Parliament Jo Cox in 2016.

Yet extraordinarily, Usman Khan and his Al Qaeda mates were not deemed to be in that category. They'd only plotted to commit mass murder, to train terrorists, to assassinate politicians, to kill and main civilians in pubs and clubs – and were caught before they got the chance to do any of it.

So Khan gets out after eight years, and of course, then gets the chance to do what he had craved for many years.

It's an absolute disgrace that he was released.

In America, if you're a convicted Al-Qaeda or ISIS operative, you're led to a small cold foreboding window-less cell and you don't come out again. Pictured is Guantanamo Bay where terrorist prisoners are held

Just as it was an absolute disgrace that most of his other accomplices were released too, including Mohibur Rahman who was let out early after applying to a deradicalization program but was jailed again in 2017 for plotting a 'mass casualty attack' on a police or military target, receiving a minimum 20-year sentence.

It's an even bigger disgrace that Britain continues to have a legal system that views Al-Qaeda and ISIS terrorists as little more dangerous than armed robbers.

Like Jack Merritt and Saskia Jones, I firmly believe in rehabilitation of offenders, and in giving people a second chance.

But not for everyone.

Some criminals are so dangerous they have to be treated differently to others.

And those who willingly and ideologically embrace terrorist groups like Al Qaeda and ISIS deserve nothing but the treatment they get in America.

Britain's gone weak on terror because our cowardly politicians have allowed the do-gooder, hand-wringing PC brigade to neuter down our sentencing of terrorists to the point where there is little disincentive for them to stop plotting committing terror attacks.

Al-Qaeda and ISIS terrorists don't change their spots.

And even if some of them do, I don't see why we should take the risk.

Usman Khan looked like he had, then launched a terror attack.

They should never be let out of prison.