FOLLOWING its publication in England in February, John Charmley’s biography of Winston Churchill comes to the United States on a gale of argument which is sure to continue. What he has done is to challenge two of the most sacred postwar Anglo-American myths: that the war against Hitler was justified, and that Churchill was a prescient leader in peace, and a magnificent one in war. Mr. Charmley’s verdict is different: the war cost Britain its inheritance, and Churchill, while rhetorically magnificent, was as erratic in war as he had been in peace. The distinct impression is given that Churchill lost Britain the empire it was his life’s ambition to preserve. Triumph and tragedy, indeed.