On 29 November 2019, Jack Merritt and Saskia Jones were murdered in a terror attack at a conference held in central London to celebrate the fifth anniversary of the prison education organisation Learning Together.
Former convict Rosca Onya remembers Jack Merritt, his teacher, mentor and friend.
For his whole life, Rosca always felt like an outsider. A child refugee fleeing conflict in his native Democratic Republic of Congo, he lost his parents at a young age and travelled through three different countries before arriving in England at the age of nine.
"Primary school was extremely difficult because I couldn't even speak a word of English," he says. "School was traumatic for me… kids in school used to pick on me and bully me."
He joined a local gang, became involved in crime and at the age of 18 was convicted for possession of a loaded gun. He was given an indeterminate sentence for public protection and served nine years.
It was towards the end of his sentence that he met Jack Merritt - and finally felt like he had found a place where he belonged.
"Jack was someone special and he's always going to be close to my heart. It's a beautiful thing, because I wish more people could go through the process that I've been through," 29-year-old Londoner Rosca told BBC Radio 4's Law in Action.
Jack, who had an MA in law from Cambridge University, was a course convenor for Learning Together.
This innovative project brought Cambridge undergraduates together with serving prisoners in three institutions to study criminology alongside each other.
'Jack gave me a voice'
Speaking to Law in Action in the spring of 2019, Jack described how working with prisoners had changed his perspective.
"I do truly believe that there is a difference between learning law in a classroom and engaging with the law in your real life," he said.
"I felt when I was a student that I was learning about access to justice and I was learning about law. But I never got a chance to practise justice or to interrogate that with my actions."
Rosca was one of many prisoners who benefited from Jack's influence.
"Learning Together is about giving people a voice. And Jack Merritt definitely gave me a voice in every single thing that I want to do. He just encouraged me that I can do it. He said you can be whatever you want."
In November 2019, the organisation held a conference at Fishmongers' Hall at London Bridge.
Usman Khan, who had been released on licence from a sentence for terrorist offences, fatally stabbed Jack Merritt and Saskia Jones and wounded two others at the event, before being shot dead by police.
Rosca was on his way to the conference when he heard the news.
"My phone started ringing and it was my probation officer.
"She mentioned that Cambridge University Learning Together had been in touch and asking where I was.
"I got to the bridge, and it was locked off. And all I could see was chaos going on."
He was devastated by the loss of Jack, who had become a guiding light in his efforts to turn his life around and move away from crime.
"It's extremely hard for me, I'll be honest with you, because me and Jack were not just friends… me and Jack were like brothers in that course, that we managed to do in prison.
"And after prison, he managed to stay in contact with everyone - writing them letters and keeping us level-headed. So it's extremely hard to sometimes not have him there."
At Jack's funeral, Rosca, who had always been interested in music, came up with the idea of recording a song in tribute to his friend.
"I made a promise to everyone there that I was always going to keep Jack's name alive. To pay tribute to Jack. And the only way I know how to do that is through music."
The changes Jack wanted now happening fast,
His name is the future and a bit of the past,
He lives on strong with the lessons he taught,
He lives on strong in every thought.
(Jack by Rosca)
Like almost all prison rehabilitation programmes, Learning Together is currently suspended because of the elevated risks of coronavirus in a closed environment.
But Rosca hopes that his song will keep the memory of the programme - and of Jack - alive.
"I've never met a person like Jack in my whole life. Someone that doesn't see in colour, someone that doesn't discriminate, someone that wants to be fair, and he wants everyone to just be on an equal level and give people like myself a second chance.
"So I just want to keep the legacy alive."
If you, or someone you know, have been affected by bereavement, you can find more information and support on the BBC Action Line website.