We now advise people to lie...
While at university, my best man's son applied to join up and fly Harrier jump jets . The system could not get hold of him fast enough and although he was 2 years into a 4 year engineering degree they pleaded with him to drop it and join up now. Sensibly he declined until he had completed his studies.
On joining up he submitted to a flying medical during which he admitted having been concussed during a game of school rugby while a 14 year old. He was shown the door instantly as apparently flying medical standards are quite exacting and it seems that their Lordships are unwilling to take anything other than perfect specimens.
Several years earlier, I underwent the preliminaries for flight training too to fly helicopters; square pegs in round holes, pat yer head and rub yer tummy at the same time but then admitted to having had hay fever. The actual remark made to me was 'Oh well, never mind, try again next year.' So when I eventually joined up I became a clearance diver and somehow failed to mention anything about hay fever, my theory being that although grass might grow on aircraft carriers, it certainly doesn't grow underwater. I had the last laugh because specialist diving pay was higher than flying pay.