During Irving's lawsuit against Deborah Lipstadt, Keegan — whom he had subpoenaed to appear as a witness — lambasted Irving by saying: "I continue to think it perverse of you to propose that Hitler could not have known until as late as October 1943 what was going on with the Jewish people" and, when asked if it was perverse to say that Hitler did not know about the Final Solution, answered "that it defies common sense". In an article in "The Daily Telegraph" of 12 April 2000, Keegan spoke of his experience of the trial, writing that Irving had an "all-consuming knowledge of a vast body of material" and exhibited "many of the qualities of the most creative historians", that his skill as an archivist could not be contested, and that he was "certainly never dull". However, according to Keegan, "like many who seek to shock, he may not really believe what he says and probably feels astounded when taken seriously".