It varies. I might begin by researching specific events, situations and people that interest me. I might already have a basic idea or it might only be a feeling about ‘something to do with such-and-such’. When I think I have enough understanding, I begin to write. I find it’s important to do this rather than wait too long – because the danger with research is that there is no finish line.

The research continues while I write – and even when the first drafts of the story are complete. There might be issues I’ve set aside to deal with at that stage because I know they can wait, or I may have come up with another idea that I want to check out.

Usually the physical settings for my novels are places I already know well. But not always, in which case I have extra work to do. I had to visit what was then the Soviet Union in order to get the locations and settings right for Patriots. That was a bit of a challenge, as there were so many things and places that you were forbidden to take photos of – not just obvious places like military establishments or security headquarters but also transport infrastructure such as roads and rail lines, and even bridges and rivers. Meanwhile you could take all the photos you wanted of Red Square! But I went ahead and took my chances. I also studied Russian (most of it now forgotten), partly to be able to talk to people whose help and input I needed, and partly to give as accurate a flavour as possible to the dialogue in the book