" The next morning, Tuesday, Churchill worked on it some more, but found his concentration broken by the sound of hammering coming from construction underway in the Horse Guards Parade, where workers were busy shoring up the Cabinet War Rooms (later named the Churchill War Rooms), situated in the basement of a large government office building a short walk from No. 10 Downing Street. At nine A.M. he ordered Colville to find the source and stop it. “This is an almost daily complaint,” Colville wrote, “and must cause considerable delay in the measures being taken to defend Whitehall. "

― Erik Larson , The Splendid and the Vile: A Saga of Churchill, Family, and Defiance During the Blitz