I think this IS an incredible find, because i don't think i ever saw the helicopter from this angle. I think that this scene and Freddie walking is not from the Doro recordings, and that indicates that at least there is footage from backstage from Knebworth that i wasn't aware of in TV archives.
If the media recorded a song or two from the concert, then i think this is a great find.
I supose this is the BBC? - Maybe they could contact them to see how much still exists.
Thanks for bringing this to my attention.