Yesterday was the anniversary of the arrest warrants issued by the International Criminal Court (ICC) for Ahmad Harun and Ali Kushayb for atrocities in Darfur, Sudan. Their names mean little to most of us, while those of Fred West and Harold Shipman have become shorthand for mass murder. Yet the crimes of these serial killers belong to a pre-industrial age.

Adam Smith, the Scottish economist, believed that the division of labour was one of the great engines of material progress. Look at the pin-maker. In the past one man could make one pin per day. But now? “One man draws out the wire, another straights it, a third cuts it, a fourth points it, a fifth grinds it at the top for receiving the head... Making a pin is... divided into about 18 distinct operations.” Mass murder, too, requires modern management techniques: a chain of command, delegation, specialisation, co-ordination, even public relations.

I have just returned from visiting Auschwitz-Birkenau and Belzec with a Holocaust survivor, Kitty Hart-Moxon. She survived in Birkenau for eight months, maybe 50ft away from the screams coming from Gas Chamber and Crematorium No 4. She worked in the Kanada Kommando, sorting through the belongings of the victims; collecting jewellery for the SS and clothes for bombed-out German civilians.

As a prisoner, Kitty was coerced into the camp machinery. Above her towered a dizzying and sometimes chaotic hierarchy: from SS Rapportführer Taube, Lagerführer Hössler, the camp commandant Rudolf Hess right up to Obersturmbann- führer Adolf Eichmann, and the fractious empires of Heydrich, Himmler, and Göring.

The numbers of people needed to commit mass murder is inversely correlated to the technologies employed. In Belzec, a small compound 886 sq ft in area, 150 SS guards took only nine months to gas half a million people, including Kitty's grandmother.

In Rwanda, up to 120,000 people were mobilised to kill 800,000 people in 100 days. In Darfur, another low-technology atrocity, maybe 20,000 Janjawid militiamen, and a smaller number of regular soldiers, killed more than 200,000 people.

Not only do we not prevent mass murder, neither do we punish the perpetrators afterwards. For every uncaught Jack the Ripper there are thousands of mass murderers still at large. Only one SS guard served four and a half years for his role at Belzec. The number of Cambodian perpetrators currently on trial can be counted on one hand. The ICC will only make a small dent in impunity: it has the capacity only to conduct maybe six investigations and a handful of trials between 2007 and 2009.

Small teams of men tracking down and capturing war criminals is largely the stuff of fiction. The real work is done behind the scenes: threatening to withdraw bilateral aid unless suspects are handed over, untangling extradition requests, creating specialist police units and domestic legal reforms to allow extraterritorial jurisdiction over international crimes. Most of all, the problem is not finding suspects but taking the many small steps to create the political will to prosecute them.

The UK has an opportunity to take one of these small steps in June. Like Eichmann, the Sudanese government minister Armad Harun is suspected of being one of the middle managers of mass murder. It took real management skill to cajole disparate militias, and the Sudanese Army and Air Force, to conduct hundreds of separate attacks across an area the size of France. These skills were rewarded with promotion: Harun is now Minister for Humanitarian Affairs, in charge of feeding the victims of his own suspected crimes.

The international community's response to this defiance has been to do nothing. Nor has it acted against Kushayb, the former Janjawid leader.

This June the UK will play a key role on the Security Council, helping to guide its response to the ICC prosecutor's next report on Sudan. Last time, China blocked a presidential statement on the ICC. This time, with China absorbed by the Olympics, the UK should take the lead and introduce a resolution imposing asset freezes on all Sudanese government officials harbouring Harun and Kushayb. Any future discussions of debt relief or bilateral aid for Sudan should also be made conditional on handing over the two men for trial.

The international community has spent a long time on the “architecture” of international justice and has neglected the “plumbing”. We've built an impressive list of treaties and international tribunals and courts, while neglecting enforcement and apprehension.

The UK has done more than most, providing funding for many international courts and tribunals and making a tentative start in searching for war criminals now living in the UK. British diplomacy was crucial in the arrest of Slobodan Milosevic; the day after he was surrendered the international community pledged $1.28 billion in bilateral aid to Serbia. Without British leadership this time it's likely that, like Kitty, in 40 years' time an intrepid survivor will be returning to Darfur to tell her story. Meanwhile, in a quiet dictatorship somewhere, the elderly killer of her mother will be quietly living out the end of his days in luxury.

Nick Donovan co-ordinates the Aegis Trust's Wanted for War Crimes campaign

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