A spy, like a writer, lives outside the mainstream population. He steals his experience through bribes and reconstructs it.
If I started at 13, by the time I was 14 I was already good enough to play in front of people. I started off playing drums when I was 5, so playing in front of people didn't matter - not a problem.
I started off like everyone else does, slogging but having a compulsion to put words on paper. I didn't write or read horror or fantasy, other than children's fantasy, until I was in my teens.

