I dozed for a couple of hours as the train made its way through south-eastern Germany, arriving in the German capital around twenty minutes before midnight. I dialled an Uber and had that take me to the old 'West Berlin'. The Cold War was over, but most western operatives still based themselves in the west of the city. I needed the key first, visiting another local contact, before I found myself walking into a bus station on the edge of the city.

Ensuring I was unobserved, I opened the locker and retrieved the duffel bag. There was an EU identity card with my photo on it. Said I was French,...