It is just short of 30 years since the collapse of the Soviet Union and suddenly there comes a reminder of how the world used to be. A member of staff at the British Embassy in Berlin has been arrested in Germany on suspicion of spying for Russia. The arrest took place in Potsdam, which used to be in East Germany, and the Glienecke Bridge separating the town from Berlin proper is where Cold War spies used to be exchanged.