He chose as his subject the secret negotiations between Adolf Eichmann and the Jewish leaders in Budapest, Joel Brand and Rezsö Kasztner, the so-called "trucks for Jews" deal, and British knowledge of the scheme from codebreaking. He has researched the topic extensively in Allied archives for both his Churchill and his Himmler biographies.

Despite precautions, the Austrian political police are believed to have learned of the visit by wiretaps or intercepting e-mails. Mr Irving had privately visited his embattled friend the German playwright Rolf Hochhuth on the way to Austria; they had not met for twenty years because of travel restrictions imposed on each of them