I began to see there wasn't much future in this subject. Many people carry on what they start in their PhD, they then go on because particularly as the world was opening up in those days, there was new opportunities. So I left Cambridge in '52, '53.

[Q] There was still... you did some work on haemoglobin?

Yes, because I had to wait, I was going to go to America to work with David Sayre in 1952 after my PhD but I couldn't get a visa to America because the South African authorities had given me a black mark. They wouldn't give me a certificate to say that I hadn't been... I hadn't... I was not guilty, that's the word they use, no... no... I can't remember the phrasing it all was but that there was nothing, moral turpitude in my career. It was a... it was a way that... it was during the McCarthy era you see and I'd been a... a member of the Student Liberal Association when I was a student and that was regarded by the then apartheid authorities as being a sort of Communist, I was against them. I had thought myself as a socialist in those days but only in a theoretical way and I was certainly anti-Communist, this I knew very well about Stalin's dictatorship and so on; I read a good deal of political books and I read a lot of history, contemporary history and so on, it was very political, South Africa, at the time. And so... so, of course I couldn't go to America, so I spent a year in the College Science Department because [FJW] Roughton, Professor of College Science who worked on the interaction of oxygen with haemoglobin wanted somebody to try to understand how oxygen diffused into a red blood cell. Because it was then diffusing and at the same time interacting with... interacting with haemoglobin. And so the technique I'd worked – partial differentiation with a chemical change – I was easily able to adapt my programmes, the EDSAC programme to do all this. And then later on I came to work on... and I became interested in haemoglobin and worked out the... some, published... in fact, I published very little on this but I did work out the consequences of the Adair equation where you have four stages in haemoglobin oxygen uptake. And... and... it was... I managed to estimate the rate constants for the uptake of the four oxygens, which were 4,3,2 and 80. So 4,3,2 is statical: 4321. But the 80 showed the phase change and that showed that the phase change was in the last uptake of the last oxygen. So this gave me an interest in biology.

[Q] So did you come into contact with Max at all?

No... no... that was in the College Science Department but I used to go... I was around when I saw the DNA and I...I used to see Cochran and Crick quite a bit, not Crick, Cochran and Wolfson; I actually published a few papers on... one main paper on the determining phase in X-ray crystallography. It's a rather lengthy abstract paper, which had some influence later on, probability distributions, X-ray intensities was from which you could do phasing. It influenced Gerard Bricogne later. I could have... I... I could do this kind of applicable mathematics but I... One of the things I learned later, you have to deny yourself not to do some things in order to do others, you see, you can't just... you know, do anything that comes to your mind, there's a kind of lesson there.