Just found this thread.
Back in 1974, a Maj Keck, USAF Police, equivalent to the RAF Regt. He told how USAF guards used to stand until the new college grads said how they could do a better job, in a deck chair, under a shade, with shades and a cool pack. They could see UNDER the aircraft they were supposed to be guarding rather than standing with their backs to the kite.
By proper deployment they covered their 6 and stayed more alert. Needless to say he didn't take their word for it but tried it out. It worked.
In Malaya in 1964 the RMAux Police used to 'hide' too. Very effective.
Standing up as a target is a very good early warning of attack but not necessarily very bright.
As for ASI, as Beagle said, I had a Chevette but only CBFASI, OC Admn and Slops wore caps, oh an SLATS, SNO, and BASI.