In fact the big issue is security clearances. Certain roles are out of bounds because it isn't possible to obtain a full security clearance.
Well now then. I had DV and clearances above DV. So I had 'full security clearance' (which doesn't actually exist - you have BPSS, SC, DV and certain other ones which I shall not mention).
Maybe I am a thick Oirishman and didn't actually work in those roles for years then