So BA chose to involuntarily downgrade the nanny who happens to not have any BA elite status? Perhaps the "high-flyer couple" should keep in mind a lesson from high-flying elite status holders in the business travel world: there are benefits to getting "the staff" -- particularly "critical" facilitation "staff" -- frequent flyer program status too.
Does ageism and sexism ever play a part in how BA chooses to select a customer for involuntary downgrade? I suspect at times it has done just that.