Simon Norton died last week. I got the news yesterday.
I have written about Simon here before, after reading Alexander Masters’ biography. I have no intention of rehearsing Simon’s eccentricities. But he had an extraordinary talent and insight into mathematics, especially finite group theory; nobody knew their way around the Monster like Simon.
How did he do it? Especially, how did he see a group like the Monster? Masters’ book doesn’t tell us, since it doesn’t explain what a simple group is. Now Simon can’t tell us.
I have always thought that mathematicians’ thought processes offer us a unique insight into the way the human mind thinks.
In any case, Simon is a sad loss; the world is poorer without him, not just mathematically.
Peter Cameron's Blog 
This is very sad indeed. I asked Simon something about the Monster as recently as last year, and he replied that he might look into it… R.I.P.