I had changed from being a mathematician to a practicing scientist. I was increasingly embarassed that I could no longer follow some of the more modern branches of pure mathematics.

I am delighted to have had students, friends and colleagues in so many nations and to have learned so much of what I know from them. This Nobel Award honours them all.

Leaving England was a painful decision, and we still have some regrets about it. However, at that time, the research environment for theoretical chemistry was clearly better in the U.S.

In the war, most young men were inducted into the armed forces at the age of 17. A group of students was permitted to attend university before taking part in wartime research projects.

I was a close observer of the developments in molecular biology.

At the age of 12, I developed an intense interest in mathematics. On exposure to algebra, I was fascinated by simultaneous equations and read ahead of the class to the end of the book.

I have had many opportunities to visit universities all over the world in the past 50 years.