I hadn't thought of that. In fact, I haven't thought of Edmund Cooper for years (must dig him out and re-read, especially The Overman Culture). I thought he was just trying to make a big flashy sparkly picture with lots of bits that people like, such as steam trains and balloons. And that certainly worked for me. If there had been a sensical explanation for why London was that way, I would have been far more intrigued and interested.