The Third Reich has been rehashed and repackaged so many times that some are starting to think Britons have an unhealthy fascination with it.

But, says Huw Richards, experts believe there is still much to discover about the period.

Several television channels would have had to invent them had they never existed, but the German ambassador thinks Britain has an unhealthy fascination with them. Seventy years on from the Nazis coming to power on January 30 1933, is there anything more we need to know about them?

Few, if any, historical subjects have been more extensively researched and written about than the Third Reich. Michael Burleigh wrote, in the introduction to his The Third Reich: A New His tory (2000): "The subject of one chapter in this book is the object of more than 55,000 titles."

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The scale of the literature reflects the worldwide impact of Nazism, the horrified fascination that it still exerts and the scale of the archives bequeathed by its crash in 1945. Much, of course, is the endless rehashing and repackaging of familiar themes, contributing nothing new to the subject.

Neither do the history shelves in bookstores necessarily reflect the best current research and writing, any more than the bestseller racks encapsulate cutting-edge literature. But some books achieve both academic and popular impact - none more in recent years than Ian Kershaw's two-volume 1,960-page life of Hitler, Hubris 1889-1936 (1998) and Nemesis 1936-45 (2000).

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Kershaw, professor of history at Sheffield University, therefore speaks with authority when he says that there is still much serious and important work being done.

Several forces can drive research in a crowded field. One is the simple availability of archives. And here Kershaw points to the impact of the fall of communism in Eastern Europe. "It opened up enormous archives in Central and Eastern Europe that had previously not been readily accessible to scholars, creating the opportunity for fine work, in particular by younger German scholars." He points to particular vitality in studies of Nazism in regions such as East Prussia that were lost to Germany after 1945, making the archives inaccessible. SS leader Heinrich Himmler's appointments book came to light in Moscow, while the astonishing diaries of Victor Klemperer, a Jew who managed to survive the war while living in Germany, emerged from East Germany.

Richard Evans, professor of history at Cambridge University, is currently working on a history of the Third Reich and describes the Klemperer diaries as "a hugely important record of the period. For Klemperer, the diaries were a reason to carry on living in dire circumstances and under ever-increasing pressure from the regime. There's no doubt there's still a lot to be found in East European archives."

But changes in intellectual fashion can be as important an influence as the availability of sources. It is now second nature to regard the Holocaust as the central fact of Nazism, but it was not always thus. Kershaw points out that academic interest in the first 25 years after the war emphasised the 1930s more than the 1940s and tended to focus on how the Nazis gained power rather than what they did with it. "There was earlier interest in themes that are now less popular, in some cases reflecting the conflict between Marxism and Liberal Democracy in the division of Germany. In the 1960s, Marxists were particularly preoccupied by the relationship between Nazism and big business."

Evans says: "A stress on the class elements of Nazism has given way to an emphasis on race as a central factor. Nazism is increasingly seen as a comprehensive project to revise the racial order of Germany and Europe. The extermination of Jews is central, but also part of a wider pattern where homosexuals, other alleged racial inferiors such as Gypsies and Slavs, the 'asocial' and the mentally and physically handicapped were also slaughtered."

It is not that the Holocaust was not unknown in earlier years. The Nuremberg trials, concluded in 1947, broadcast the evidence, while Gerald Reitlinger published The Final Solution as early as 1953.

Yet Kershaw recalls: "It took a while before we started to get serious explanations. Debate started in Germany in the 1960s and 1970s with some good research, and the Eichmann and Auschwitz trials stirred up academic interest. But it took longer to reach public consciousness."

He says that the US TV series Holocaust , broadcast in the late 1970s, accomplished the breakthrough: "The word itself was not so common in those days. It was in many ways an awful piece of television, but it grabbed popular attention, not least in Germany."

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Kershaw is less enamoured with another catalyst - David Irving's Hitler's War (1975) and its claim that Hitler was unaware of the slaughter committed in his name: "It provoked Martin Broszat, one of the leading German history professors into a brilliant critique, in effect an annihilation of Irving's thesis. It created a storm in Germany and increasing awareness of the centrality of the issue."

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That awareness is now highly productive. "Christian Gerlach has shown how calculations of the extent to which Germany could feed its population help explain the way the Holocaust developed. Peter Langerich of Royal Holloway has shown how it developed in a series of escalations, while Peter Witte's work on the Himmler diaries provides vital light on the emergence of the Holocaust," Kershaw says.

Himmler and his lieutenant Reinhard Heydrich are the subjects of forthcoming academic biographies. There has always been a market for potboilers on the SS, but Kershaw says: "A few years ago it would have been regarded as highly eccentric to write a scholarly biography of either Himmler or Heydrich."

Changing fashions again provide the explanation. "In the 1970s and 1980s there was a tendency to regard the perpetrators as faceless bureaucrats who were doing a job", says Kershaw. "The focus has now switched to looking at the ideological commitment of those involved."

The benefits of biography are exemplified by German historian Ulrich Herbert's life of Werner Vest. "Vest was the head of the Nazi administration in Denmark and was previously one of the SS's leading ideological thinkers. He was an SS lawyer," says Kershaw. "He went to university in the early 1920s, soaked up the sort of radical racism that Hitler represented, in particular the idea of the racial cleansing of Germany, and put it into practice in the SS and in Denmark."

The extent to which Vest represented an archetype was demonstrated by Michael Wildt's remarkable collective biography of the architects of the Holocaust, Generation of the Unbound: The Leadership Corps of the Reichssicherheitshauptamt . "These were people who were not only the planners, but did the killing themselves," Kershaw says. "Wildt found a number of people who were at German universities in the 1920s, many doing doctorates, who were convinced ideologues and in the 1940s found themselves able to put that ideology into practice."

Contemporary events also affect views and emphases. Sociologist Michael Mann's comparative examinations of ethnic cleansing and the Holocaust are clearly linked to recent events. While acknowledging the reasons for the use of such moral and judicial concepts in examining Nazism, Evans argues that they are not always ideal tools for historians, moving them away from the priority of explaining why events happened.

There are, however, much greater worries than this. Readers will notice that almost every contemporary historian mentioned in this article, other than Kershaw and Evans, is German. It is, of course, inevitable that Germans will be central to the study of Nazism, but it might be hoped that their salience in the British school syllabus, television schedules and other media would generate a flow of young British historians anxious to add their insights.

"There's no shortage of good undergraduates, but when they get to postgraduate level they are handicapped by a lack of languages," explains Kershaw. "Their German counterparts speak good English, often French and increasingly, East European languages."

Kershaw finds more and more that postgraduates, and applicants for academic jobs, are non-British. When Nik Waschmann, author of a study of Hitler's prisons - which, as Kershaw points out, had more inmates than the concentration camps until 1943 and were a vicious part of the apparatus of oppression - was appointed to a post in German history at Sheffield, there was only one Briton on a five-strong shortlist.

Evans concurs with Kershaw's worries about language skills, and notes an intriguing response by many Cambridge undergraduates to the dominance of Nazism in the school curriculum. "They've had enough of it by the time they get here," he explains.

Kershaw admits with wry good humour that he can hardly complain about some consequences of this overconcentration. "It is good for business," he says, but he worries that it is at the expense of other areas of historical knowledge. "You have good students who have a detailed knowledge of Nazism but are worryingly uninformed about their own country's history or the aspects of German and European history that would put that knowledge of the period between 1933 and 1945 into context."

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He finds himself in the unusual position of an academic arguing that school pupils should study his specialist subject less than they do. It is clearly time, as the German ambassador has argued, to get the Nazis into a more realistic perspective.