HE was a short, plumpish academic-looking man in his sixties, with a neat beard and walking stick, clearly uncomfortable among the prawn canapés of a trendy central London hotel.

In this world of peacocks and poseurs, he stood out by not standing out. Quietly spoken, with a Belfast brogue softened by a childhood in south-east England, he drew little attention to himself. Which was, no doubt, why Patrick Magee could pass unnoticed as he toured the United Kingdom in 1978, planting 16 bombs in various cities and, then again, in 1984, when he blew up Brighton’s Grand Hotel during the Conservative party conference, killing five people.

Among his victims that night was Tory MP Sir Anthony Berry. His daughter Jo was also at the party, sipping wine and chatting to the inquisitive crowd. The body language between them was awkward but not overtly hostile. On first-name terms, they had clearly spent quite a bit of time in each other’s company since they first met in 2000, often at events like this one: last month’s launch of the documentary film, Beyond Right and Wrong, exploring the subject of forgiveness.

Beyond Right and Wrong is a fascinating title — with obvious shades of Nietzsche’s Beyond Good and Evil — because it captures something of the complex moral ambivalence many of us feel towards forgiveness.

Magee did 14 years in prison, released in 1999 under the terms of the Good Friday agreement. Some continue to feel that this punishment was not enough; that, on some level, he got away with it.

It is a similar uneasy feeling one can have with forgiveness itself, that it undermines the basic logic of proportionality that underpins most moral thinking — that the scales of justice require some sort of balance. Crime needs to be offset by a proportionate amount of punishment. An eye for an eye, a tooth for a tooth. Forgiveness ignores all of that, which is why it exists beyond right and wrong.

Yet the problem with the retributive model of justice, constructed as it is upon the moral instinct for proportionality, is that it can easily serve to perpetuate violence and hatred — one act of violence leading to another in response, which can provoke yet another, and so on.

The blood feud that can exist between families is the most striking example of how answering violence with violence can be a potentially endless business, with old hatreds forever spawning new ones.

Politicians who support amnesty arrangements such as the Good Friday agreement are often upbraided for betraying the past.

But what Jo Berry is more interested in is how the instinct for revenge can easily become a betrayal of the future.

Her forgiveness of Patrick Magee is quite extraordinary, taking huge courage and emotional poise. And she admitted to me that she sometimes goes for a walk on the beach in north Wales and smashes rocks against each other in frustration. This is a safe detonation of the anger she feels inside. She says that for all to move on and reclaim a more peaceful future, these feelings have to be left on the beach.Too often, forgiveness is construed as miraculously having positive feelings towards the person who had harmed you. This understanding is, I suspect, an impossible fiction. But what is not impossible is the refusal of revenge, the refusal to answer back in kind.

Beyond Right and Wrong examines powerful stories of ordinary people in Rwanda and Israel/Palestine who have let go of perfectly natural punitive instincts in the name of a brighter tomorrow, one not trapped by the hatreds of the past. One might also note that, in Christian terms, it is this same sacrifice that puts the good into Good Friday. — The Guardian, London

The writer is priest-in-charge at St Mary’s Newington in south London.