According to the photographer this was the first movement off Runway 13 after the extension was opened. Note how there are no leading edge lift devices and also, compared to modern aircraft in this class, the large amount of take-off flap used. Also noticeable is the clean exhaust of this R-R Conway powered model compared to the smokey JT3D examples back then.
This photo was added on 3 January 2022, and has since been viewed 400 times.