If I had lost a family member on Bloody Sunday in Northern Ireland in 1972, I am sure I would want someone brought to justice. Nor would I care when. Indeed, though ardent about forgiveness and rehabilitation, in such a case I am sure I would want punishment. I am human, and revenge is a human emotion – though I would call it “justice”. But such justice must be subject to two limitations. One is that it should be blind and impartial; the other is that justice should to some degree be proportionate over time. Costs are relevant. Life must move on. The government’s decision this week to declare an amnesty in Northern Ireland and close down charges against the soldiers involved in Bloody Sunday was driven by such limitations. Guilt may be clear to some, but half a century has passed. Unjustified killings are not uncommon in war, not least in so-called “wars among the peoples”; witness the continuing cases against British troops in Iraq. Here the accused are old men, and convictions in such cases are hard to achieve. The Northern Ireland minister, Brandon Lewis, has proposed a general amnesty for crimes committed during the Troubles prior to the 1998 ceasefire. He suggests a “truth and reconciliation commission” based on the model used in South Africa and elsewhere. Allegations will be investigated – there are some 1,200 deaths being examined by the Northern Ireland police – and information gathered and digested, but without fear of legal reprisal. A border museum and memorial are even proposed. It will come as no surprise that Lewis’s proposal has satisfied none of the parties involved in the province – except, we assume, the British army. Ireland does not do amnesties. The issue was so sensitive as to be left out of the Good Friday agreement in 1997. There was instead a confused array of pardons and prison releases, causing the Democratic Unionist party to oppose the agreement. That left the field open for eternal litigation as victims on both sides played out the Troubles through the courts. In the past decade alone, some 1,000 cases have consumed most of a staggering £500m in legal aid, despite, according to Lewis, “almost never providing the families with the answers or result they seek”. A courtroom is a better place to achieve victim satisfaction than a Belfast backstreet, though the dilatory fashion in which the legal process has proceeded is outrageous. Even so, Lewis’s proposal may be sensible. A truth commission must be preferable to an everlasting stumble through a costly judicial jungle. Diverting the present costs of litigation to a relief fund would surely be a better use of public money. Victims are preferable beneficiaries than lawyers. Northern Ireland’s rival communities remain defined by their past. Ever since the Protestant “plantations” of the 16th and 17th centuries, not a generation has escaped some form of communal conflict, often with extremes of atrocity unknown on the British side of the Irish Sea. The entire country is a memorial to an evil act of past English monarchs, the attempt to eradicate Irish Catholicism by colonial settlement. The modern legacy of that attempt is unequivocally England’s fault. The obligation on its present governors – and they are still British – is to do everything to move on. Boris Johnson’s pledge to the DUnP over the Northern Ireland Brexit protocol may have been rooted in a lie. But the lie – that there was no need for a barrier in the Irish Sea – may just have pushed the country a step nearer an accommodation with the south, initially on trade but inevitably on other areas of sovereignty. Militant unionists will always oppose any amnesty for the IRA. Longstanding hostility is their reason for existing – as it is that of the IRA. But militancy is clearly losing electoral support. Polls show opinion is now neck and neck on moves towards reunification, with opposition softening even among Protestants, while Sinn Fein continues to cleanse its image and strengthen in the south. What the country most desperately needs is to put past conflicts behind it. It needs to deploy that much underrated quality in any nation’s history: the ability to forget. The obstacle to forgetting in Northern Ireland is carved across the hills and fields of its border with the south, a standing memorial to communal division. It is replicated in the city of Belfast’s “peace walls”. That anywhere in 21st-century Europe should feel the need for such barriers between its citizens is a blot on the politics of the British Isles. These barriers, physical and metaphorical, are the ones that truth and reconciliation should confront. But the best news out of Northern Ireland would be for the “forget party” to win through, to see virtue in a future united Ireland. If so, it is to be hoped that Lewis’s commissions, memorials and museums may be consigned not to memory but to oblivion. Simon Jenkins is a Guardian columnist