in 1987); and Franz Stangl, commandant of Treblinka (sentenced to life imprisonment in West Germany in 1970). Many of the remaining 60,000 were in their twenties in 1944-45, when the worst atrocities were being committed, so would now be in their eighties. Statistical analysis suggests some 5,000 are alive today. They include Alois Brunner, Eichmann’s right-hand man, now thought to be living in Syria.

How did so many get away?

In the chaotic aftermath of the War, Nazi sympathisers established a series of escape routes, known as "rat-lines", for war criminals fleeing Europe. One rat-line, the Odessa ("Organisation of Former SS-Members", made famous by Frederick Forsyth's The Odessa File) was run by Hitler's favourite commando, Otto Skorzeny, who went on to advise Argentine dictator Juan Perón about setting up a Fourth Reich in Latin America. Another led through Rome, a favourite destination for Nazi "pilgrims", where they were helped by a number of high-ranking Vatican officials. A notable example was Austrian bishop Dr Alois Hudal, who felt it his "duty" to prevent German fugitives from falling into Allied hands and made a secret pact with the Italian police to take wanted Nazis (including Eichmann, Stangl and Gustav Wagner, deputy commandant of Sobibor) to selected churches and monasteries.

And where did the war criminals go?

Many beneficiaries of Bishop Hudal's charity ended up in Argentina, where Perón welcomed them. In fact the Argentines also set up rat-lines of their own through Scandinavia, Belgium and Switzerland. Scores of unrepentant Nazis were given top jobs under assumed names as technicians in the Argentine armed forces. Meanwhile the Swiss government – for the sum of 200,000 Swiss francs per Nazi – helped others to fly on regular scheduled flights to Brazil, no questions asked. (For a higher fee, Swiss bankers quietly transferred vast sums from Zurich to Brazilian banks.) Right-wing military dictatorships in Paraguay, Chile and Uruguay were other havens. News about Aribert Heim may also point to the role played by anti-Israeli regimes in the Middle East, notably Egypt and Syria, in giving sanctuary to war criminals.

What was done to stop escapes?

In the aftermath of the War, Allied leaders were acutely aware that many war criminals remained at large, but found it hard to follow up leads. Many of the most notorious criminals, including Eichmann, Josef Mengele and Heim, were in Allied custody for a time but were released for lack of evidence and uncertainty over who they were. The War Crimes Invest-igation Team, formed in April 1945, had only 11 officers. But in recent years, less savoury reasons for the Allies' failure to prevent escapes have emerged; similar charges have been levelled against the KGB. And today, the case of Aribert Heim has put Germany under the spotlight. If his family were well aware that Heim was living in Cairo, why was it so hard for the German authorities to discover that fact?