Doing Aeros in a Vampire T 11 over a quiet bit of Norfolk ( I thought ) with my student. As we came over the top of a loop, looked forward to see the Lightning’s of the Firebirds ( the RAF aerobatic team then) in close formation opposite direction, dead ahead at the same height and VERY close. Grabbed the stick and pulled hard which flicked us into an incipient spin as we shot underneath them. Shut the throttle and centralised the stick and we flopped over into a dive. Long shuddering breath and sweaty palms!