Christopher Hampton's stage adaptation of George Steiner's novel The Portage to San Cristobal of A.H. at the Mermaid in 1982 gave McCowen a great final speech, an attempted vindication of racial extermination delivered by Adolf Hitler, which for Guardian critic Michael Billington was "one of the greatest pieces of acting I have ever seen: a shuffling, grizzled, hunched, baggy figure, yet suggesting the monomaniac power of the Nuremberg Rallies, inhabiting the frail vessel of this old man's body." It was a performance that also won him his third Evening Standard Best Actor award, a record equalled only by Laurence Olivier and Paul Scofield.