Was this before erstwhile Harrier candidates were given some initial hovering experience in helicopters? During my time instructing on the Gazelle, Harrier Pilots got a few sorties hovering at 50 feet, using purpose laid ground markers. Not a favourite pastime of us QHIs because it meant protracted operation in the avoid curve.
Watching that film (which I was first shown around 1977, during BFTS training on the Jet Provost) reminds me of a later open day at RAF Odiham when a cocky young Harrier pilot, who had flown from the OCU for a static display, was talking to a young lad, aged about five, and his mother. The young lad, in his innocence, pointed to the “outrigger” undercarriage legs and asked the Harrier pilot when they would allow him to take off his stabilisers. The lad obviously had them on his bicycle.....so it was obvious to him that a trainee Harrier pilot must have them, too!