During the elaboration process, I get a lot of my ideas from research. In the case of Victorian bankers, I read books about how Victorian bankers failed, how they succeeded, what their houses were like, the domestic problems that they might have had, whether they got divorced, how they did their courting when they fell in love, and so on. And all those research topics give you ideas for dramatic scenes.
In the case of Eye of the Needle, I was writing about a German spy crossing England during the war. It was important then to read about catching trains, trying to get petrol for a car, security checks and so on. Every bit of research that I did would suggest a scene in which the main character is confronted by a problem and has to be resourceful and courageous to over come it. The whole thing is teased out in this way.
I gain inspiration from the research, but I am always working my imagination to elaborate the story. I often use the services of professional researchers, mainly Dan Starer of Research for Writers in New York. Dan produces reading lists on, say, earthquakes, clones or eighteenth-century criminal courts. He finds learned articles, out-of-print books and old maps, people for me to interview, experts and historians, detectives and FBI agents. Most of my books are checked for factual errors before publication by at least one technical consultant.