When MVD officials are posted to a Soviet Embassy in the West, what measures if any are taken to discourage their defection? Are their children over a certain age held in the Soviet Union? If the official is single, is he allowed abroad? Is [sic] any of his relations nominated as hostages? Does source know of an instance where action has been taken against the relations in the USSR of an MVD official who has defected? Are defections publicized or explained?

MI5 Questionnaire for Vladimir Petrov,

April 1955

It was a classic case where a spur-of-the-moment defection so frequently goes sour. The guys who have done best are those who worked in place for a long period of time and then come over with some preparation.

Bob Gates in Sell-Out by James Adams