Grant cannot understand how she can let go of her "right" to revenge. "By not meeting you, the man who raped you still has the power over you. He's winning," he warns her, almost paternally. "If he were dead, you'd feel differently, trust me."

Boyce, now a counsellor and life-coach, lets it pass. This isn't about preaching or winning the point. It is about making people think. "All I can tell you," she says, "is that I don't wake up now thinking about him. I have no emotion about him. I'm getting on with my life, enjoying. I even like men." 

There is a nervous ripple of laughter as the group try to digest this, but Grant wants the last word. "Then he's escaping too easily," he insists. Boyce may not have won them all round, but most have made a start.

Before Boyce starts her talk, the project's facilitator, ex-convict Peter Woolf, goes round the circle to ask what everyone is expecting of the three days. Quite a few reply that they have come as part of their "sentence plan". They are ticking boxes in the hope that it will increase their chance of parole. Some just want something to do. "I've come because it's better being in here than being stuck in my cell with all my pent-up anger," announces Nigel, one of two inmates in the group who have been recalled to prison after breaking the terms of their early release. "I hope," he adds, playing to the gallery, "that I can find it in me to forgive the police who sent me back here." Most, though, are more serious and admit that they are not sure what forgiveness is, but have been intrigued by a preparatory talk given at High Down on behalf of the charity back in November by the parents of the murdered London teenager  Jimmy Mizen.

Participants are split into small groups. "Let's be honest," says Tommy (halfway through a long stretch for gun crime), "most of us try not to think about our victims. The way I get round it is to tell myself they all had guns as well, so they knew what could happen." Geoff from Liverpool, the most articulate of the group, immediately challenges this. "That's like blaming them, saying it's their fault you shot them. I've been inside for 13 years and in that time I've blamed everyone from my mum, my dad, my drug dealer, my girlfriend, the drugs, but in the end I've ended up with me as the one to blame." The switch in focus from Boyce's story to their own is under way. 

Day two of the workshop involves participants working with the facilitators to map out on large sheets of paper their own "lifelines". This account of their childhood, family and crimes they then share with the others. It touches some dark places, and demands the sort of openness and trust that my presence as an observer might inhibit. "In prison," explains Cantacuzino, "daily life is all about avoiding appearing vulnerable. Here in the workshop, some people talk about themselves in a way they haven't been able to before in prison."

When I return for the third and final day at High Down, the atmosphere is noticeably different when we start off by going round the circle for reflections on how it has been so far. Even the sceptics are shifting their position. "I came here to get out of my cell," acknowledges Nigel, "but what I have heard has really touched me. If forgiveness can help Rosalyn so much, perhaps it can help me too."