Photocopy of a diary kept during February 1944-April 1945 by the Director of the British Branch of the American MIT Radiation Laboratory (BBRL), containing a detailed record of his contacts and discussions with British radar scientists (notably Robert Watson-Watt, A. P. Rowe, Bernard Lovell and other scientists at the Telecommunications Research Establishment at Great Malvern) and U. S. Air Force commanders with regard to the development and use of a wide variety of radar systems, including 'Oboe', 'Loran', 'Gee', H2X, MEW and SCR-584, the implementation of radar in the run-up to and during the Normandy landings in June 1944 and its subsequent use in the French, Italian and German theatres of war. Also includes interesting comments on the V-1 and V-2 weapons and the methods of defense against them; other German 'secret weapons', and Trump's interviews with German radar scientists in April 1945.