Tin Pot
Guru
It's for life. You can, and will be improsoned for revealing any secret information. Hence why finding a real story from a real SF serviceman are few and far between. Anyone bragging is usually talking shite and they stand out like a dogs dick.
You'll know the real ones. They carry themselves in a certain way. I can't describe it. Very powerful men.
Information about classified operations of course, but is prior membership of the regiment actually classified?
Unless you're denying the existence of the regiment, which they aren't, I can't see any reason it would remain classified. Perhaps to protect them?