In 1958, age 15 I went to Hornchurch when applying for an RAF Scholarship (money to see me through A levels). Did the aptitude & medical tests and interviews. On Day 3 about a third of us (the others went home) were bussed to Cranwell where we did a further 3 days of the oil barrel over crocodile infested water etc. exercises, interviews, 15 minute presentation etc. As another has said, you could easily identify the Public School educated ones. An entertaining week off school during GCE Revision.
A month later got a letter saying declined on medical grounds. I am pretty short sighted, I'm amazed I made the initial cut. Left school aged 16, spent a year as an industrial chemist and then joined as a direct entry Air Radar Fitter. Left 9 years later as a Sergeant to do Meteorological Research and ended up running an Oil Industry SME. I wonder what a career as an Engineering Officer would have been like in the 60s through the 80s if I has made it.