Cambridge University graduates Ms Jones, 23, and Mr Merritt, 25, were attacked during a prisoner rehabilitation event at Fishmongers’ Hall last Friday afternoon.
Convicted terrorist Khan, 28, who was living in Stafford, was later identified as their killer.
Armed with two knives and wearing a fake suicide vest, he was tackled by members of the public, including ex-offenders from the conference, before he was shot dead by police.
Mr Merritt, from Cottenham, Cambridgeshire, worked on the programme associated with Cambridge University’s Institute of Criminology which is aimed at bringing offenders and people in higher education to “study alongside each other”.
A statement from his family said: “Jack Merritt, our beautiful, talented boy, died doing what he loved, surrounded by people he loved and who loved him. He lit up our lives and the lives of his many friends and colleagues, and we will miss him terribly.
“Jack lived his principles; he believed in redemption and rehabilitation, not revenge, and he always took the side of the underdog.
“Jack was an intelligent, thoughtful and empathetic person who was looking forward to building a future with his girlfriend, Leanne, and making a career helping people in the criminal justice system.”
Ms Jones, a volunteer on the programme from Stratford-upon-Avon, Warwickshire, was described as having “great passion” for providing support to victims of crime by her family.