Well defruiter - I've never been broken off when i've told ATC I can't comply!! As I said, I'll do what I can to help out, fly the speed I'm asked to - but if I can't then I won't... If YOU can't sort out the traffic behind then that simply is not my problem
Besides - if you did break me off to fit in someone behind and above then I'd be on the blower to your boss fairly pronto
