Re: Ah memories...
Actually Illuminati was designed by a different Steve Jackson (an American rather the brit Steve Jackson in the article).
To complicate matters still further both Steve Jackson's actually wrote Fighting Fantasy books (though it was the brit from the article who founded the series with Ian Livingstone).
Weirdly enough there's no distinction on the FF books for either author, both were just credited as Steve Jackson on the front of the books.
Wow - I'm boring myself now!