I heard her quick steps coming over, and then she opened the door abruptly and stuck her head out. She looked extremely cross, and yelled at me: ‘What the hell do you think you’re doing? I thought you were ignoring me, so what’s all this shouting?’ Then she shut the door with a bang without even giving me the opportunity to get a word in edgeways, as if it wasn’t her that was bothering other people, but me who had come to disturb her. I was so cross that I was about to kick the door open, but thinking better of it I controlled myself.

‘You see – how can anyone work with someone like that?’ Comrade Chen complained. ‘You bring this Bodhisattva here, and not only does she not do anything to help, she makes everyone else’s life more difficult. How are we supposed to crack this cipher? To tell you the truth, after all this time I don’t have the slightest idea of how to go about it. I simply don’t have any feel for this at all.’

I tried to cheer him up. ‘It doesn’t matter; that’s normal. Modern ciphers are always very difficult to get started on, but once you’ve found a way in you’ll be fine.’

Anderov used to say that modern ciphers aren’t mazes, they are black holes. You can get into a maze but you can’t get out, so even though you can’t crack the whole cipher you can crack individual intercepts, because it doesn’t matter where you enter, there is only one way to go. A black hole you can’t get into, and if you do there are hundreds of different paths through it, so the problem is finding the right one – which is much harder than finding your way out of the most complex of mazes.

When Comrade Chen said that he didn’t have a feel for this at all, I wasn’t surprised. I knew that the reason that Huang Yiyi wanted him to take part in the cryptanalysis work was because she needed a scapegoat, just like shock troops and mine-clearers on the battlefield. You send them out to die, using their flesh and blood to clear the obstacles and find the traps so that their comrades can pass without danger. Otherwise how can you expect your troops to go and assault mountain fortresses and win?

That wasn’t the problem. The problem was that Comrade Chen was a much respected cryptographer in Unit 701, and from start to finish he didn’t know what his real role was in this working group. Even after Huang Yiyi cracked RECOVERY, he still didn’t know. For decades after, I felt bad for old Chen for that reason.

Of course, that all happened much later … we’re talking about Huang Yiyi.