I could see £10/TP for BA so a £15k requirement for Gold and £30k for GGL renewal and, on the topic of this thread... £1m for GGLfL!
I imagine if you put your mind to it then you could probably get GGLfL for £250k total spend at the moment?
But I guess most people who get there would have spent significantly more, either personally or via their company, or a combination of both.
A key question would be how many TPs they would let you earn from Amex spend?
All pure conjecture at the moment, of course.