Margaret Thatcher, prime minister of the United Kingdom from 1979 to 1990, was one of the most prominent, and divisive, national leaders in the final phase of the Cold War. In this talk I will draw on my most recent research project that re-examined aspects of 1980s science and science policy in the UK as revealed in the working documents of Thatcher. She intervened on several important issues, and, sometimes, her scientific education and early career work experience as an industrial chemist mattered. I will focus on international topics, specifically policies on acid rain, the ozone hole, climate change, CERN, and strategic missile defence, as well as events such as the Chernobyl incident of 1986. I will also review key developments in science diplomacy, and science in international relations, relating to UK interests, in the period before Thatcher.