In the spring of 1959 I won a National Science Foundation fellowship that enabled me to do physics anywhere I wanted to. I chose Paris. I had spent the last couple of years at the Institute for Advanced Study in Princeton and wanted very much to go to a city. Murray Gell-Mann was paying a visit to Princeton at the time. I had written a paper with a colleague suggesting how an idea of Gell-Mann’s could be tested experimentally. He dropped round to my office and asked what I was doing the following year. I told him. To my surprise he said he was going to Paris too, and added: ‘Stick with me, kid, and I’ll put you on Broadway.’ I didn’t then tell him that I was familiar with him from another life.

In the early 1970s I wrote a profile of Albert Einstein for the New Yorker. I had known his secretary Helen Dukas since my days at the Institute for Advanced Study. She had come with him when he emigrated from Germany and lived in the Einsteins’ house in Princeton, which after his death she shared with his stepdaughter Margot. I asked if I could visit the house. She agreed. In Einstein’s study there was an etching of James Clerk Maxwell and one of Newton which had come out of its frame. This seemed symbolically correct. Helen offered to make lunch and while she was preparing the sandwiches she gave me a book to look at. It included a letter Einstein sent from Brussels to his wife Elsa in 1930.