The CHAIRMAN (Lt.-Colonel H. S. Rogers, C.M.G., D.S.O., M.I.Struct.E.) welcomed the large audience which filled the lecture hall and overflowed into the Council and Committee rooms on the ground floor (which had been connected by loud speakers with the microphone on the reading desk) and included representatives from the Home Office, the War Office, the Air Ministry, the London County Council and Scotland Yard, as well as the immediate past President of the Institution of Civil Engineers. He was highly gratified that so many had come to listen to the paper and it was evident that the subject which the lecturer was to deal with aroused widespread interest, amongst engineers. A telephone message had been received from Sir John Anderson (the Lord Privy Seal, and Minister for Civil Defence) expressing regret that a debate which was taking place at that moment in the House of Commons prevented his being present. He understood that Mr. Helsby had condensed his paper in order to allow time for a discussion, and he therefore introduced the lecturer without further preamble.