A University of Cambridge graduate who was killed in the London Bridge terror attack "dedicated his life to helping others".
Jack Merritt, 25, was a course coordinator at Learning Together, which organised the prison rehabilitation conference attended by Usman Khan before his deadly rampage on Friday afternoon.
It has emerged that Khan, 28, was a convicted terrorist who was wearing an electronic tag after being released half-way through a 16-year prison sentence for plotting to bomb the London Stock Exchange.
British rapper Dave paid tribute to Mr Merritt on Twitter, describing him as "the best guy".
"Rest in peace brother," he wrote. "One of the most painful things.
"Jack Merritt was the best guy. Dedicated his life to helping others, was genuinely an honour to have met someone like you and everything you've done for us I'll never ever forget."
Mr Merritt's father also paid tribute to his son, who studied law at the University of Manchester before attending the University of Cambridge from 2016 to 2017.
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David Merritt posted on Twitter: "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.
"R.I.P. Jack: you were a beautiful spirit who always took the side of the underdog."
He added: "Jack lived his beliefs. He held me to a high standard; he would have expected me to say this, and would have pulled me up had I not!
"He was an exceptional young man, and I'm only finding out the half of it now he's gone."
"I don't feel inspirational, but Jack was," he added.
Criminology lecturer Serena Wright responded to David Merritt's tweet, writing: "I knew your son through Learning Together & I loved him to pieces – he was the sweetest, most caring and selfless individual I've ever met.
"The warmest heart, always with time for anyone. Completely irreplaceable – I will mourn his loss greatly and honour his memory."
Others who met Mr Merritt have posted tributes on social media.
Legal commentator and journalist Joshua Rozenberg, who interviewed Mr Merritt about the course he ran, described him as a "fine young man, dedicated to improving people's lives".
Barrister Tim Storrie said he had met Mr Merritt at Warren Hill prison and praised his "open heartedness, his drive and his faith in the redemption of prisoners through education".