How would the airport know if a pilot in uniform is flying or not
As we all clearly understand. If you turn up at staff search, in uniform, accessing airside using your ID. You are declaring you are operating/on duty.
That declaration is easily confirmed by a simple check of one's roster.
God help the first one checked, who's roster shows them to be on a day off!
I imagine the high security facility at Belmarsh might correctly be the destination for most airport workers attempting that?