The AEC invited the British government to send representatives to a series of meetings in Washington, DC, on 27 and 28 August 1958 to work out the details. The US delegation included Willard Libby, AEC deputy chairman; Loper; Brigadier General Alfred Starbird, AEC Director of Military Applications; Norris Bradbury, director of the Los Alamos National Laboratory; Edward Teller, director of the Lawrence Livermore Laboratory; and James W. McRae, president of the Sandia Corporation. The British representatives were Sir Frederick Brundrett, the Chief Scientific Adviser to the Ministry of Defence, and Victor Macklen from the Ministry of Defence; and William Penney, William Cook and E. F. Newly from the Atomic Weapons Research Establishment at Aldermaston. The Americans disclosed the details of nine of their nuclear weapon designs: the Mark 7, Mark 15/39, Mark 19, Mark 25, Mark 27, Mark 28, Mark 31, Mark 33 and Mark 34. In return, the British provided the details of seven of theirs, including Green Grass; Pennant, the boosted device which had been detonated in the Grapple Z test on 22 August; Flagpole, the two-stage device scheduled for 2 September; Burgee, scheduled for 23 September; and the three-stage Halliard 3. The Americans were impressed with the British designs, particularly with Halliard 1, the heavier version of Halliard 3. Cook, therefore, changed the Grapple Z programme to fire Halliard 1 instead of Halliard 3. Macmillan noted in his diary with satisfaction: