On arrival in London, Bohr rejoined his father, who had flown to Britain the week before.[10] He officially became a junior researcher at the Department of Scientific and Industrial Research, but actually served as personal assistant and secretary to his father. The two worked on Tube Alloys, the British atomic bomb project. On 30 December 1943, they made the first of a number of visits to the United States, where his father was a consultant to the Manhattan Project.[11] Due to his father's fame, they were given false names; Bohr became James Baker, and his father, Nicholas Baker.[12] In 1945, the director of the Los Alamos Laboratory, Robert Oppenheimer, asked them to review the design of the modulated neutron initiator.