I've never forgotten a Battle of Britain day at Biggin Hill in the 60's. The Lightnings had done a bomb burst or similar manoeuvre and were reforming to the north - except that two of them had sneaked round to the south and came up the valley behind the crowd and came over the top of us at about 200 feet, probably with reheat because I can still picture blue flames coming from the jet pipes. No-one saw them coming, only going away, fast.
It was like being hit over the head with a sledgehammer! Made a lasting impression on a 12 year old lad.