He collected the cars and wrote about the (non-fictional) drugs. He wasn't an exhibitionist, as far as I know, so you'll have to infer what you like about the middle one from his writing.
Some related reading:
https://www.theguardian.com/books/1997/may/20/fiction.scienc...
https://www.scotsman.com/news/interview-iain-banks-a-merger-...