Noisy, this would be because the Southside is in the Controlled Zone as opposed to the Restricted Zone (which requires a valid pass and a full search). Bottom line, no doubt, was probably avoiding paperwork!
That's a pathetic excuse mate, and you know it. We're not talking a few numpties in Extras or a foreign mil crew. These guys couldn't be less of a risk to security considering that after their sojourn in their present job, they'll be flying front line fighters defending this country.
What will the Dept for Tw4ts do if a Fat Albert divs into Briss and has to sit on 30L cos it's tech? They'll have a pink fit "oh I'm terribly sorry chaps but you can't have your Herkybird back as it happens to be in the Restricted Zone."