He was Emeritus Professor of the History of Mathematics and Logic at Middlesex University, and a Visiting Research Associate at the London School of Economics.

[5] He was a fellow at the Institute for Advanced Study in Princeton, New Jersey, United States, and a member of the International Academy of the History of Science.

Grattan-Guinness gave over 570 invited lectures to organisations and societies, or to conferences and congresses, in over 20 countries around the world.

These lectures include tours undertaken in Australia, New Zealand, Italy, South Africa and Portugal.

[1] He was especially interested in characterising how past thinkers, far removed from us in time, view their findings differently from the way we see them now (for example, Euclid).

He did extensive research with original sources both published and unpublished, thanks to his reading and spoken knowledge of the main European languages.