The father of one of the London Bridge terror victims said he doesn't want his son's death to be used as an excuse for 'draconian sentences'.

Grieving David Merritt made the remark hours after 25-year-old son Jack was fatally stabbed by terrorist Usman Khan.

Khan, 28, also killed a woman, who has not been named, and injured three others during a five-minute deadly rampage on Friday lunchtime.

Dad David has described Cambridge University graduate Jack as someone who "always took the side of the underdog".

Writing on Twitter, he said: "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 for detaining people unnecessarily.

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(Image: Facebook)

"R.I.P. Jack: you were a beautiful spirit who always took the side of the underdog."

He wrote that his son had been a "champion" for those who had "dealt a losing hand by life, who ended up in the prison system".

He also tweeted: "Jack spoke so highly of all the people he worked with & he loved his job.

"Thank you for your support. I know his colleagues are in shock- please look after each other at this terrible time."

Jack, from Cottenham, Cambridgeshire, was a course leader for the prisoner rehabilitation programme, Learning Together, which had invited Usman to a conference at Fishmongers' Hall to mark the initiative's fifth year.

According to his Facebook profile, he graduated in law at the University of Manchester and went on to study at the University of Cambridge.

Before university, he attended Hills Road Sixth Form College in Cambridge.

His Instagram page is filled with photos of recent travels with his girlfriend and pals, while his Twitter feed contained a number of tweets that were critical of Tory government policies, including cuts to the criminal justice system.

Jack worked at Cambridge’s criminology department and ran Learning Together courses for offenders in prison and in the community for those who were on release.

As part of the programme, students based at Cambridge and students based in prison study together on university-level courses.

(Image: Instagram)

Khan knifed five people before he was tackled and disarmed by brave witnesses and then shot dead by police at point-blank range.

He was armed with two kitchen knives, one of which was reportedly taped to his hand, and wearing a fake suicide vest.

One of the three survivors was upgraded to stable condition on Saturday after initially being rushed to hospital with critical injuries.

A second person was stable and a third had less serious injuries. All three remained in hospital.

A source told PA that Khan started "lashing out" in a downstairs room of Fishmongers' Hall, on the north side of the bridge, but was grabbed by the conference-goers and bundled out of the front door as he tried to go upstairs.

He is said to have threatened to blow up the building.

(Image: PA)

Around half a dozen members of the public, including a convicted murderer who was attending the same conference, a Polish chef who worked at the hall, two tour guides and an off-duty police British Transport Police officer worked together to stop and disarm the attacker.

Despite being stabbed in the hand, the chef hit Khan with a 5-ft long narwhal tusk he grabbed off a wall inside the hall. Another man sprayed the terrorist in the face with a fire extinguisher.

One of the people who helped tackle Khan was James Ford, who was jailed in 2004 for the motiveless murder in Kent of 21-year-old Amanda Ford, who had the mental age of a 15-year-old.

Ford, who was jailed for life with a minimum term of 15 years, had been invited to the Fishmongers' Hall on day release along with Khan, students, staff members, alumni and representatives from the Ministry of Justice.

Khan struggled as he was pinned to the ground until armed officers arrived and shot him in front of dozens of witnesses as traffic came to a grinding halt on the bridge over the River Thames.

Police said he was acting alone. Tonight, ISIS claimed responsibility and said he was one of its fighters.