How can a dead person have a heartbeat? It is counter-intuitive, and fundamentally cryptography is massively counter-intuitive. Why do I say that cryptography is the most heartbreaking and difficult work in the world? Well, under normal circumstances a cipher cannot be cracked in anything under its set secure time, and so it is normal not to be able to break a cipher. It is decryption that is unusual. The secret workings of Heaven cannot be revealed, but if it is your job to discover them, your destiny from that moment on is heartbreaking and difficult. That means that our cryptographers had to possess absolute calm – an ability to keep their self-possession in the face of heartbreak and difficulty – as part of their psychological make-up. If, faced with someone pretending to be arrogant you become all confused and forget your own position, doing all sorts of menial tasks to try and please him, then your character is more than a little weak. How could someone like that convince me that the future would be bright? You must understand, at that time the first glimmers of the bright dawn we were looking for seemed as fine as gossamer, and at that time we were still in the midst of the storm. It seemed that perhaps only if we stayed as still as a corpse, not becoming alarmed whatever happened, not changing no matter how alarming the situation, day after day, night after night, that we might get a lucky break.

Of course cryptography is a branch of mathematics, and a profound and incisive mathematical capability was just as important and necessary as the right kind of psychological make-up. The two worked together like a pair of wings, and one without the other would be no good. I wasn’t sure whether my method for testing their mathematical capabilities was entirely scientific and logical, for it might well turn out to be arbitrary and favour certain candidates unfairly. But I was absolutely sure that my assessment of their psychology was accurate. It was my principle that I would rather have a lack than a surplus, I didn’t want too many people; in this context lots not necessarily being a good thing, while a few was not necessarily a bad thing either. Therefore I insisted on selecting the candidates in my own way, and of the twelve people I saw in the first round, I chose six who would sit the written paper.