Dave Wilson That was the "manning the mast" ceremony at HMS Ganges, the RN boy training establishment, originally a wooden hulk moored in Mylor Harbour, near Falmouth, but latterly a shore establishment at Shotley in Suffolk.
All the boys had to go up the mast at the beginning of their course. That let me out of a naval career, 35,000' in a nice comfy Victor is one thing, 150' up a flipping mast is quite another
Have a look at this if you're brave!