Roger and Kate Starte are civilians.
According to the blurb on the dust jacket of the first adventure, the author and his wife left in 1956 to take part in a journey by jeep into the countries behind the Iron Curtain and eventually into the Soviet Union. Soon thereafter, however, they were reported as having been evicted by the Russians, the exact reason being not clearly stated. Upon his return to England, Williams drafted the first story but released it as a work of fiction.
So, the question remains whether the activities contained in the two novels are novelizations of real events or whether the trip just spurred the imagination of a writer and an enjoyable story resulted.
Whichever the truth may be, the two novels should be required reading for spy fiction fans as they contain some of the best gritty and despondent descriptions of life under totalitarian regimes. Even granting a considerable amount of pro-Western bias on the part of the drafter, the fear of betrayal and the desperation of the people are fascinating. While both the Startes are definitely amateurs, they are both very intelligent and very cunning. Things happen behind the Iron Curtain which surprise them but they keep their heads on straight and stay alive.
Interestingly, the events of the book, The Borders Of Barbarism, were used in a 1966 episode of the Ben Gazzara drama series Run For Your Life. In the tele-drama, the luscious Joan Collins convinces Gazzara's character, Paul Bryan, to escort her into Yugoslavia to find jewels her father had buried during the War. They travel as a married couple out to photograph birds.