This is remarkable news. I'm somewhat in shock and feel extremely sorry for Mark. In my humble opinion (FWIW) he's been shoddily treated by Neil for a great many years. As much as Neil can often be extremely gracious and humble - and is clearly well-liked by a great many people - I think the way he's treated Mark over most of CH's career has been a real blot on his record.
I will, of course, continue to show an interest in everything he does but he seems keen to chip away at the CH legacy with every turn.