The mother of a man killed by a convicted terrorist at a rehabilitation conference in 2019 told an inquest on Monday that her son was a force for good in the world. Usman Khan fatally stabbed University of Cambridge graduates Jack Merritt, 25, and Saskia Jones, 23, and wounded two others at the London event before being shot dead by police on London Bridge. Merritt's mother, Anne, told the opening day of the nine-week inquest that her son's life was a triumph, even if his death was a tragedy. "Jack Merritt was a good person,” she told a jury. “Jack was a force for good in the world, someone who made other people's lives better for knowing him. "We are hugely proud of who Jack was and what he stood for. His death was a tragedy but his life was a triumph." Khan, 28, was out on licence when he attended the event organised by the university on November 29. The extremist served a prison term after being found guilty of being part of a group that plotted to bomb London's stock exchange. Last year, the family started legal proceedings against the government over the management and assessment of Khan's risk to the public before he was released. The family of Jones, 23, said they wanted the focus of the coroner and the jury to be on the evidence before them. They said that she did incredible research in the field of sexual violence and planned to become a detective specialising in victim support within the police force. The hearing is expected to be followed by a separate jury inquest into the death of Khan. A UK watchdog last year called for extremists to be given lie detector tests, arguing that deradicalisation programmes do not work. Jonathan Hall QC, the UK’s independent reviewer of terrorism legislation, said there was “no magic bullet or special pill” that could help to change convicted extremists.