I was a co-pilot on a Trident back in the ’70s when all three of us on the flight deck saw what appeared like that in the video. London Radar called us to ask if we could see anything in our “11 O Clock”. Yes we could and had been discussing it for about 10 seconds. It then moved Eastward into our 12 O’clock (dead ahead) and shot off up the North sea.
London radar commented that what ever it was it was too fast for his equipment for him to track it as it accelerated at an enormous rate , presumably to a very high speed. We all saw it, said agreed to contact the Radar unit after landing, BUT , strangely we never discussed it after landing. Not something I have shared with many people.