Technically, I have been taught aerobatics by a former RAF display pilot in a warbird.
Ok it was a lovely old Chipmunk but that type has been used on spy flights to take photos of Soviet army exercises. Does that count ? I don't know of any instances where a Harvard has ever been in harms way but others will be able to comment. For the record, I was solo in my cockpit, he was solo in his. (I was marked as "above average" in my training records but my good friend was probably being extremely generous.)