Carl Kaysen: Economist, author and special assistant to John F Kennedy

Instructed by my supervisor, the Canadian economist Harry Johnson – his students, such as Amartya Sen, later a Nobel Prize winner and master of Trinity, Mahbub-ul-Hay, later of the World Bank, and the rest of us reading Part II Economics, did as we were told – I attended a series of lectures by Carl Kaysen.

He had been recommended to the economics faculty of the University of Cambridge by the visiting American Professor of the Year, Milton Friedman.

Unforgettable. Without notes this tall, elegant, bow-tied and extremely well-dressed 35-year-old, in contrast to other scruffy but hugely distinguished colleagues, held forth on the Trade Cycle. Roy Harrod, Michael Kalecki, Franco Modigliani and other gurus of the 1950s were clinically assessed. Every so often, he would pause and say, "is that clear – have you any questions?" Some perceptive undergraduate, often Jagdish Bhagwati, later professor of economics at Columbia, would ask an erudite and involved question. Kaysen's responses were models of clarity. Asked for her opinion, an earnest, as we thought, Newnham undergraduate, favoured protégé of Ruth Cohen, later Mistress of Newnham, blurted out, "Carl Kaysen," – pause – "was the most handsome and attractive man that I have ever set eyes on!" We understood.

Kaysen grew up in Philadelphia, graduating in 1940 from the University of Pennsylvania. Posted to London in 1941, he worked on identifying the targets on the European mainland where bombing could do most damage to the Nazi war machine. Returning to the US, he worked at the National Bureau of Economic Research and then went via graduate study at Columbia to Harvard, where he completed his doctorate in 1954. He was appointed associate professor, then to a full professorship in 1957, and then associate dean of the Graduate School of Public Administration.

It was from this position that he was plucked out to serve in high positions under President Kennedy. As deputy special assistant for national security affairs he is credited with being the brains on the American side when the Partial Test Ban Treaty was being formulated. When he left, Kennedy praised him for the very qualities which we as students had recognised when he had come to Cambridge eight years previously – an astonishing ability to sift through a large amount of material and present it in a form that made the decision processes much simpler and more precise. Kaysen was at the heart of US decision-making during the Berlin Wall crisis, and of the responses to the dreadful situation in the former Belgian Congo.

In 1966, at the age of only 40, he was selected to succeed J. Robert Oppenheimer as director of the Institute of Advanced Study at Princeton. After 10 years he moved to become professor of political economy at the Massachusetts Institute of Technology, and contemporaneously vice-chairman of the Sloan Commission on Higher Education (he was also their director of research). He was an administrative super heavyweight.

Amazingly, the books written by himself or co-authored continued to flow. In 2003, by then a mid-octogenarian, Kaysen published War with Iraq: Costs, Consequences and Alternatives. As a strident opponent of Tony Blair's decision to endorse Bush, I found Kaysen's contribution the most powerful and succinct of any text. He asserted that Bush and Blair had connived to "invent the war for a perfectly implausible purpose".

When I wrote him a letter saying how useful and powerful his book had been, I received a friendly but acid reply: how had people like me allowed a situation in which Bush, whom he despised, could say, "but, look, a Labour – a Labour Prime Minister in Britain – is supporting me!" Kaysen was sad that a country where he had served in the Second World War, and with whose University of Cambridge he had so many connections, should have egged on Bush's Washington in such a catastrophic foreign policy.

Carl Kaysen, economist and public policy adviser: born Philadelphia 5 March 1920; deputy special assistant to the President of the US, 1961–63; David W. Skinner professor of political economy, Massachusetts Institute of Technology 1977–90, then Emeritus; married first 1940 Annette Neutra (died 1990; two daughters), second 1994 Ruth Butler; died 8 February 2010.