The Sri Lankan civil war lasted for a quarter of a century, until the decisive defeat of the Tamil Tigers in 2009. In the dying phases of that conflict, war crimes were committed by both sides, but the Sri Lankan government has refused to accept that its forces took part in the murder of civilians.
That is why David Cameron came under pressure to pull out of this week's Commonwealth Heads of Government Meeting in Colombo. Douglas Alexander, the Shadow Foreign Secretary, and British Tamil organisations argued that the UK's refusal to attend would put pressure on the Sri Lankan government to co-operate with a United Nations investigation into war crimes. The UN says that 70,000 civilians were "unaccounted for" at the end of the war, and Human Rights Watch says that Sri Lankan armed forces have continued a campaign of harassment and torture of Tamils since the end of the fighting.
That was an argument which persuaded Stephen Harper, the Canadian Prime Minister, who pulled out of the summit on Friday, and which seems to have persuaded Manmohan Singh, the Indian Prime Minister, who pulled out yesterday. In his case, the impact is complicated by India's history as the main external supporter of the Tamil cause and as the – unsuccessful – provider of peacekeeping forces in the late 1980s.
Yet in Britain's case, Mr Cameron's defence of his decision to attend is persuasive. Had the Government announced some time ago that it would be boycotting the meeting, it might have made a "News in Brief" paragraph in some papers and then been forgotten.
As it is, the Prime Minister feels he has to justify, at some length, his attendance, and to explain, at some length, the points he will be making to the Sri Lankan government about the credibility of its Lessons Learnt and Reconciliation process. "If I stayed away, some of the British cameras would stay away, some of the British press would stay away," he said yesterday in a broadcast on Deepam TV, a UK-based Tamil channel. "I want to take the press, the cameras with me. I want to shine a light on what has happened in Sri Lanka and put the government under pressure to do the right thing for everyone in Sri Lanka in the future."
Mr Cameron also drew attention to a Channel 4 documentary, No Fire Zone, made by the team who were nominated for a Nobel Peace Prize for previous documentaries exposing atrocities committed in the 138-day final offensive in Sri Lanka's civil war.
For much of the British and world media, including The Independent on Sunday, the debate about the Sri Lankan government's complicity in the horrors of 2009 is the main story of this week's summit meeting – although for some of our rivals Prince Charles's first outing as representative of the Queen has equal prominence.
In the eternal debate between engagement and isolation as the best way to put pressure on governments unwilling to abide by international human rights norms, we believe that Sri Lanka's case falls on the side of engagement. Boycotting the summit would certainly annoy the Sri Lankan government, but it would have done little to muster world opinion. The diplomatic pressure exerted by membership of the Commonwealth, and the attention attracted by the media circus of international summitry, offer a better hope of bringing Sri Lanka to a lasting peace based on equal rights and recognition of past mistakes.