Five years ago, scarcely a week went by without a media appearance from David Cesarani. The history of the Nazis and the Holocaust were in vogue and the country's leading specialist in Jewish history was top of every editor's wish list of pundits."It was a strange time," he recalls."The resurgence in Nazi scholarship due to the opening of the archives after the collapse of the former eastern bloc coincided with events in Rwanda, Bosnia and Kosovo. The past telescoped into the present as the world sought to understand the nature of genocide and wipe the historical slate clean before the new millennium."

Then the phone went quiet. For one thing, a greater understanding of the Holocaust did not bring about an end to genocide, and for another the events of 9/11 changed the news agenda. The west had a new set of enemies and the single-mindedness, not to mention fickleness, of the media meant that a new set of commentators got to have their week in the sun. "The book came about as a result of some research I had been doing for a TV documentary," he says."I realised there had been no biography written since Eichmann's trial and execution in the early 60s, and yet our understanding of the Nazis has moved on a great deal since then. So I felt the time was right to re-evaluate him in the light of the new historiography."

Cesarani also set out to demolish some of the myths and inaccuracies surrounding Eichmann."He wasn't the great Jew-hater of the popular histories," he points out."In his early life, he had perfectly normal, functional relations with Jews. His first employer was a Jew, and in the early years of the war he helped his stepmother's Jewish relatives escape to Switzerland. So the notion that his later crimes were born of an ever-present anti-semitism is nonsense."

The book goes on to apportion embarrassment all round. Cesarani reveals that the main reason Eichmann was able to evade discovery in Germany for five years after the war was because he deliberately chose to live in the British zone."The US zone of occupation was crawling with intelligence officers hunting down Nazis," he laughs."But the British zone had just 15 - one of whom was Clement Freud." Even the Israelis don't come out smelling of roses. Eichmann's eventual capture proved to be a masterpiece of Mossad incompetence and owed far more to the efforts of Fritz Bauer, of a member of the German judiciary, than to Israeli persistence.

But the central theme that runs through the biography is the same one that has driven much of the research into the Nazis. How could a country as civilised as Germany become capable of genocide? Cesarani is the first to admit that history is as culturally biased as any other humanity, and that the Nazis have become a universal metonym for the darkest limits of human behaviour."We could draw the same inferences from the Rape of Nanking, but somehow because the atrocities involve the Japanese and the Chinese, they don't have the same immediacy. Part of the horror of the Nazis is that it happened here in the west, in a location we think we understand."

Yet Cesarani rejects the traditionally accepted view - made popular by Hannah Arendt and others - of Germany as a country that mindlessly surrendered its morality under the sheer weight of a totalitarian machine."There was always a degree of voluntarism," he argues."Eichmann could have walked away. Until 1941, his work was fairly innocuous. He does sometimes turn the screws of terror, but nothing on the scale of mass slaughter.

"But between June 1941 and January 1942, various options opened and closed as the Nazi leaders deliberated whether the Jews were to be deported or killed. Eichmann's skills lay in the logistics, and he was desperately worried about being sidelined in the hierarchy. In the end, the Wannsee conference decided on both deportation and extermination, so Eichmann was in clover. He liked to claim that he had no choice in becoming a conscienceless killer, but the truth was he embraced it as an astute career move."

One thing Cesarani learned early on is that there is no such thing as straightforward Jewish history. In his late teens, he went to Israel to work on a kibbutz."We were always told that the pile of rubble at the top of the hill was a Crusader castle," he says."It was only much later that I discovered it was an Arab village that had been ruined in the Six-Day war."

It's a lesson he's never forgotten throughout his academic career, which has seen him move from Leeds to Queen Mary College, to Southampton - via a stint as director of studies at the Wiener Library (Britain's largest Holocaust library) - to Manchester and now to his current position as research professor of Jewish history at Royal Holloway."The study of history is shrouded in half-truths," he says."The reason the Holocaust was driven up the political agenda in the 90s wasn't only due to academic and moral imperatives. There was also an economic undercurrent: the US, the EU and the World Bank were trying to get the former Soviet Bloc countries to revamp their property laws and bring them in line with the west. This meant that minds had to be concentrated on righting wrongs."