A man who championed “underdogs” in prison has been named one of two victims stabbed to death in London as it was revealed the attacker was on early parole for a terror plot.

Jack Merritt, 25, was attending a program on prisoner rehabilitation when he was killed in Friday’s terrorism rampage in the city.

The University of Cambridge course co-ordinator has been remembered as a “beautiful spirit” who fought for people in jail.

Jack Merritt was passionate about criminal justice, according to his father. Photo: Instagram

The terrorist Usman Khan, 28, was attending the same event in Fishmongers’ Hall when he launched a frenzied stabbing attack which reached its dramatic conclusion on London Bridge.

Khan was brandishing two 20cm kitchen knives – one strapped to his hand – and wore a fake explosive belt when he launched at victims before 2pm on Friday (local time).

He was taken down on London Bridge by civilians – who have been hailed as heroes – using a stick, a narwhal tusk and fire extinguisher before police arrived and shot dead the terrorist.

It has since emerged that Khan was part of an al-Qaeda-inspired terror group jailed for plotting to target major sites including parliament, the US embassy and individuals including Boris Johnson, then the mayor of London.

Usman Khan was on early parole for a terror plot when he launched Friday’s London Bridge attack.

He was released early on parole last year after serving less than seven years of a 16-year sentence and had been living in the Staffordshire area, reportedly fixed with an electronic ankle monitor.

Grieving father David Merritt paid tribute to his son on Twitter, saying Jack was a “beautiful spirit who always took the side of the underdog”.

“Cambridge lost a proud son and a champion of underdogs everywhere, but especially those dealt a losing hand by life, who ended up in the prison system.”

UK media outlets are reporting Jack Merritt was a course co-ordinator for Learning Together, a prisoners’ rehabilitation programme which was hosting Friday’s conference.

Mr Merritt’s tweets, which have since been deleted, revealed his son “would not wish for his death to be used as a pretext for more draconian sentences or for detaining people unnecessarily”.

Jack Merritt was a graduate of the University of Cambridge. Photo: Instagram

British law commentator Joshua Rozenberg said Jack was a “fine young man dedicated to improving people’s lives”.

“I am deeply sorry to hear that Jack Merritt was murdered in the terrorist attack at London Bridge,” he tweeted.

“I interviewed him at Warren Hill prison about the course he ran for prisoners and university students.”

Criminal barrister Tim Storrie said he was “utterly lost for words”.

“I too met him at Warren Hill. His open heartedness, his drive and his faith in the redemption of prisoners through education shone out. He saved lives through his work.”

The identity of the second deceased victim, a female, has not been released.

Of the three people who were wounded, one is in a critical but stable condition, one is stable and the third has less serious injuries.

Who are the heroes?

A group of at least six men – including a convicted murderer on day release – have been praised for disarming the knife-wielding terrorist on London Bridge.

A quick-thinking man inside Fishmongers’ Hall, a conference venue at the north end of London Bridge, grabbed a five-foot narwhal tusk from the wall and used it to fight the attacker.

https://twitter.com/jamesheartfield/status/1200688631750549504?s=21

Witness Amy Coop posted on Twitter: “A guy who was with us at Fishmongers Hall took a 5’ narwhale tusk from the wall and went out to confront the attacker.

“You can see him standing over the man (with what looks like a white pole) in the video. We were trying to help victims inside but that man’s a hero.”

The unknown heroes – one with a fire extinguisher and the other with the narwhal tusk – keep the islamicist fanatic at bay.

Another hero has been identified as Thomas Gray, 24, who was driving near the scene.

“I tried to stamp on his hand as hard as I could to release the knife,” Mr Gray told ITV News. 

London Bridge Terror: Thomas Gray is one of the brave members of the public who apprehended the attacker.

He claims the suspect was armed with more than one weapon as he stabbed people around the busy central London area.

Read more: https://t.co/MtLbqt1HTX pic.twitter.com/EkqtJZXP4d

— ITV News (@itvnews) November 29, 2019

Stevie Hurst, a 32-year-old tour guide, was also driving near London Bridge at the time and jumped out to charge toward the attacker before kicking him in the head.

“I was just trying to do as much as I could to get him to release the knife,” Mr Hurst told The Telegraph newspaper.

“We wanted to kick him. Everyone was shouting.

“The knife flew away. The moment they rolled him over off his chest, they saw he had a bomb vest.

“The police arrived so quickly.  They told us ‘get the f***back’, they had rifles. They put three rounds into him.”

Another brave bystander used a fire extinguisher.

There is also controversy surrounding one of the heroes who was recognised on TV as a prisoner on release for murder.

Several UK media outlets are reporting that convicted murderer James Ford, 42, was among those who chased Khan onto the street.

He was jailed for life in 2004 for the murder of Amanda Campion, who had the mental age of a 15-year-old, and was on day release to attend the conference, outraging the victim’s family.

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What drove this act of terrorism?

Khan was released from prison in December last year subject to conditions with which police said he had been complying.

He was jailed in 2012 for his role in an al Qaeda-inspired plot to blow up the London Stock Exchange.

It is so far unclear why Khan began his rampage on London Bridge.

Islamic State has claimed the attack and says it was in response to its calls to target countries that had been part of a coalition fighting the jihadist group, according to its Amaq news agency.

The group did not provide any evidence for its assertion.

A British man whose family hails from Pakistan-controlled Kashmir, Khan was radicalised by al Qaeda internet propaganda, in particular by militant Anwar al-Awlaki, a web-savvy publicist for the Islamist cause who was killed in 2011.

When sentencing Khan in 2012, British judge Alan Wilkie said he was so dangerous that he was imposing a so-called imprisonment for public protection (IPP) indeterminate sentence of eight years.

In effect, it meant Khan would remain incarcerated as long as he was considered to be a danger to the public and that the parole board should assess whether he should be released.

But in 2011, then-Conservative prime minister David Cameron announced a review of the IPP sentencing. The IPP was abolished in 2012.

After Khan appealed his sentence, he was given a determinate sentence of 16 years – meaning he could be released after serving just half of his term.

Tributes to heroes

Prime Minister Boris Johnson praised the civilians who put their lives on the line to disarm the attacker.

“I … want to pay tribute to the extraordinary bravery of those members of the public who physically intervened to protect the lives of others,” Mr Johnson told reporters in Downing Street.

“For me, they represent the very best of our country and I thank them on behalf of all of our country.”

Prime Minister Scott Morrison slammed the knife attacks in London and the Hague as “despicable acts”.

“We are not aware of any Australians being caught up in these attacks at this stage, but we are in close contact with local authorities,” Mr Morrison said in a Facebook post.