Berlin embassy arrest: A case of old-school spying?

Spying does happen all the time, but what is fairly rare is for cases to be made public or go to trial. One reason is that the origins of the investigation are often secret – it may be that there is a spy within Russian intelligence tipping off the Brits or the Germans, but they need to be protected. Or there could have been some compromise of their communications or the way they operate – likewise, the spy-catchers would not want that to become public, so they can continue to exploit their advantage.