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.

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

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

Our children were mostly brought up and educated in the Churchill suburb east of Pittsburgh. Each summer, we took them back to England for an extended period.

I abandoned chemistry to concentrate on mathematics and physics. In 1942, I travelled to Cambridge to take the scholarship examination at Trinity College, received an award and entered the university in October 1943.

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.

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.