Yes...espionage and intelligence operations are done through foreign offices and embassies, and obviously there is clear reason behind that.Embassies and foreign office holders are immune from the laws of host country. They can't be convicted or apprehended,as codified in the international law in convention on diplomatic relations in Vienna,in 1961.the diplomatic immunity provides safe conduit for intelligence and espionage.
We have dozens of examples from cold war,when foreign offices were used to watch host country. The case of recently arrested Mr Barrets and Raymond Davis is before us.
British government can't arrest Julian assauaj even today because he has been in shelter in Embassy of Ecuador in Uk, since 2011.Britain police have no jurisdiction inside Ecuador embassy, so they are waiting for four years outside embassy premises.