When Harold Wilson and the Labour Party won the British elections in 1964, the new government, at the urgings of the Party Conference, and no doubt with some impetus from Noel-Baker who remained an Member of Parliament and had become chairman of the Parliamentary Foreign Affairs Group of Labour MPs, decided to establish a branch of the Foreign Office specifically devoted to disarmament. The government then had to find a capable and not too ideological a person to be the minister responsible for this new activity. After looking at several, Wilson’s choice finally rested on Alun Gwynne-Jones, a former army officer who had became the defence correspondent of The Times in 1961. Gwynne-Jones was appointed Lord Chalfont, enabling him to sit in the House of Lords. He was also a member of the ISS and knew of Bull’s formidable expertise in his intended field. Chalfont recognised that he needed expert assistance in his new field and enlisted Hedley Bull to be the first Director of the Arms Control and Disarmament Research Unit at the Foreign Office. Bull received two years leave of absence from the LSE and took up his new duties at the beginning of 1965.

This appointment required Bull to have access to papers which had been classified as ‘for UK eyes only’, a way of keeping them private from the Americans among others. Bull had already been thinking about taking British nationality to make international travel in Europe easier than with an Australian passport. He thought by taking this step he would facilitate his access in the Foreign Office, but what he did not know was that the Australian Government did not recognise dual nationality (except for British nationals taking up Australian citizenship), and that by taking British nationality he would lose his Australian citizenship. This was a serious matter for him but by the time he found out about it, too much water had flowed under the bridge. Bull became the holder of a British passport, which he then retained for the rest of his life despite a period of ten years in Australia (1967–77) when he was a Professor of International Relations at The Australian National University in Canberra.

Bull inevitably got into scrapes with the formal bureaucratic procedures of the Foreign Office. Believing that many papers were given security classifications way beyond what the material they contained justified, he was not above opening his briefcase while on a bus or the underground and pulling out a file conspicuously marked ‘SECRET’. On at least one of these occasions someone with high official access caught Bull in this infringement of security rules and reported him to the Foreign Office. Bull was duly carpeted and had to agree to mend his ways.

While Bull found the work of the Arms Control and Disarmament Research Unit interesting, he, unsurprisingly, did not take to bureaucratic life. He saw that he was too junior and too much of an outsider to be able ever to have a major influence on British Government policies on nuclear weapons. Therefore he did not delude himself that he had made a permanent change in his profession and working environment. Nonetheless, building the Unit gave him a chance to identify and bring in experts such as Geoff Jukes, Jim Richardson (another Australian) and Ian Bellany (all three of whom were subsequently to hold posts at The Australian National University). The post also gave him opportunities for dialogue with important foreign specialists in this field, especially in the United States. The Unit gave valuable support to the British delegation to the Geneva arms control negotiations, especially on non-proliferation matters in the years while the Nuclear Non-Proliferation Treaty was being put together. Bull’s interest in strategic defences, especially his concern that they might make nuclear weapons more usable rather than less, led him to follow this issue closely in his contacts with the Kennedy and Johnson Administrations, long before the Strategic Defence Initiative was announced by Reagan.