The idea of the SAS did seem glamorous to me before I started training for selection, but the month long process is designed to weed out people who think they are going to be James Bond. Your job is to be a professional soldier. The undercover work comes at a later date. You need to learn the foundations first. When you are admitted the regiment gives you proper training.
People too have different aptitudes.
For example, the Fijians wouldn't be any use undercover in Northern Ireland. No absolutely not. We fight, rightly, under a lot of restrictions because we have to adhere to the civil law and the paramilitaries should be treated as criminals rather than terrorist organisations. Clinically speaking, they have already won and that's why we've been there 30 years. Our opponents don't obey the same rules.