"Some of the research was done by students during tutorials and at first, you could see them thinking: 'This man is trying to justify terrible deeds; he thinks too highly of mankind.' And they would say: 'I don't believe this. Because Queen Wilhelmina had said it, and the BBC had reported it: everyone knew about the camps.' Then they read the diaries, and most of them changed their minds."

Historian Bart van der Boom picks up his book Wij weten niets van hun lot [We know nothing of their fate], for which he was awarded the Libris History Award, and reads: "One of my Leiden students who had examined the diary of a Jew in hiding, announced in a tutorial that, when she reached the last page and the diary stopped abruptly, she had wondered what had happened to him. She spent a few minutes Googling and found the answer: that nice man, his wife and their two adult sons had been murdered in Auschwitz. 'And then?' I asked her. 'I burst into tears at my computer', she said."

"It still gets to me", he says as he looks up from the book. "In some sick way, it gave me satisfaction too, because this emotion contains a snatch of historical awareness: this really happened."

Are diaries typical of people at the time?

"The writers do not represent the entire Dutch population: not everyone keeps a diary and more higher educated people keep a diary than people with less education. It's not a cross-section of the population. But writers don't just write about their own lives, they talk about other people too. They often say: 'I think it's scandalous, and so does everybody else.' All the sources suggest the same thing: there is no evidence that a majority of Dutch people thought persecution was acceptable and Jewish diarists found support rather than feeling abandoned."

But why was there so little resistance?

"There is a huge gap between their perception and ours: they did not understand certain things that are clear to us. And moreover, the Dutch are an obedient people, as you can see from the Arbeitseinsatz and war production for Germany. Their hands were tied: they didn't have any weapons and punishment was harsh. They couldn't shut everything down because that would cause havoc. The Dutch obeyed to prevent worse things happening. We might appreciate their motives for obeying things like the Arbeitseinsatz, but we can't say the same about the persecution of the Jews because, of course, there was nothing was worse to be avoided. But that is precisely what people in the war didn't know.

"There are almost no sources that reveal that people knew exactly what was going on in the camps. The East was a black hole, but it was obvious the Germans would treat the Jews badly."

For the diarists, it's evident that things did not bode well for those who were deported.

"The crux is that few Dutch people suspected, let alone knew, that the Jews were murdered on arrival in the camps. People presumed that they were forced to do hard labour in poor conditions and that many would die as a result. Wir haben es nicht gewußt meaning: it's nonsense to suppose that we had no idea that bad things were happening to the Jews. But there is a big difference between knowing and suspecting. It's easier to do something if you have actual information. And there is big difference between immediate murder and death after an unspecified time.

"It's also crucial to realise that the rumours of gas chambers and mass executions were not believed, or only up to a certain point. People knew the Germans were cruel and savage, but thought that story too awful to be real.

"Besides, there were all sorts of rumours of atrocities: descriptions that that are partly accurate were included in classic horror stories, claiming, for instance, that the bodies of Jews were used for soap. It was hard to know what to believe. It was reported, as late as March 1945, that 100,000 Dutch Jews had been liberated by the Russians. This was published by the underground press. As far as I can see, no one said: 'That's impossible - it must be wrong." For the Dutch, everything was still possible. Apparently, it was credible that they were still alive. On the other hand, after the liberation, when it was clear they were all dead, it did not come as a huge shock. Presumably, people had also taken that possibility into account too."

Imagine that everyone had known the facts. Would that have made a difference?

"It would have made a huge difference to the Jews. They tried to assess the danger; it's evident from diary fragments that some Jews chose not to go into hiding, or dithered for a long time. It's very poignant to read. Really awful."

To illustrate, he refers to the diary of Ben Koopman, a 22-year old Jewish doctor-in-training who was preparing for his forced journey for Poland. His parents had already been deported. He tried to avoid going into hiding even though he was frightened of the future. Then, on 15 May 1943, he received a postcard from his mother, in German. She writes that she and her husband are healthy and well cared for in "Werklager Wlodawa" in Poland. Koopman writes: "It is touching to read this divine postcard - it's a miracle." After all, nobody ever heard anything from people who had been deported. "My dear Moessie is in Wlodawa. May they persevere!!" After that, he waited for a knock at the door during a big raid. "Maybe then I'll see my parents again." It wasn't to be. After writing the "divine postcard", his parents were gassed in Sobibor. Ben Koopman died later in the same gas chamber.

Van der Boom adds: "It's an awful piece. He had no idea."

It is certain that Jews would have acted differently, but it is doubtful whether bystanders would have intervened if they had known.

"Maybe. I think that there were many decent Dutch people about and if they had actually known that, without their help their Jewish neighbours would be dead within a week, some would have done something. Many Dutch Jews obeyed and that did not encourage other people to resist either. In Belgium, the Jewish community consisted mostly of recent immigrants from Eastern Europe who had experienced far more anti-Semitism, didn't trust the government and more often decided to go into hiding. The demand for addresses to hide created a supply.

"Dutch authorities cooperated with the rounding up of the Jews in all kinds of ways. Remember the infamous Amsterdam 'dot map' that indicated the exact locations of Jewish homes. You have to be very cynical to suppose that, if the Germans had said to the people at the population register: 'Put it all in a map so we can gas them', all those artless civil servants would 'Yes, alright'. I can't subscribe to the view that bystanders were monsters."

There is a lot of criticism of your book, especially from Jewish circles. Former Minister Ed van Thijn says your research is misleading and Rabbi Menno ten Brink calls it "a joke". What is your opinion of their criticism?

"Ten Brink is not happy with my conclusions and his response is purely emotional. He hadn't read the book and he hadn't thought about it properly. I'm not worried about that. Van Thijn thinks that the book should be about something else, about the role of the government exiled in London. He doesn't know what to think of my conclusions. He doesn't want to think about them. I find it frustrating that I can't really get a discussion started about the research. Some people are convinced by the arguments, but feel uneasy about it. After all, it was the crime of the century, at least in the West. That guilt is crumbling because of my interpretations, and it doesn't feel right. I can understand that. But as you can see, putting a meaning on the past sometimes makes it more difficult to make sense of that same past."