[@Ace of flames01] Fine, could I say that he is at least in the Royal Marine Commando's? I know you can be there by age 19, because my friend started his training for the RMC's aged 19.

The British armed forces work a lot differently than the American. In the British armed forces, you can join the Territorial Army at 16 (With parental consent) and be fully trained by 18, to be fast-tracked into the army, then you can apply to go to almost any branch for specialist training. RMC's are one of them. The British Army's training system is a hell of a lot more rigourous, as well. American Marines take a 20 week training course, RMC's are 36 weeks. Anyone that has been accepted into the RMC's can apply to join the S.A.S. immediately, that is 32 weeks of training and is held once a year, so if you apply at the correct time, it is actually possible to get straight into the S.A.S. by 20... Not likely, because the course is hell incarnate and they can kick you out at anytime they like, without warning, should they deem you not ready for it. All I asked was for my character to be able to be S.A.S. by age 24

Should I add that he failed the S.A.S. application process a couple of times before actually being allowed to take the course?