Originally Posted by
drhandsome
I think there are two different scenarios here. There's the regular long-haul document check where they issue you a boarding pass, but you cannot board without someone checking your documents first and there's when for some reason the system finds you so suspicious that they won't even give you a boarding pass without a document check.
Sorry I think I wasn't very clear. I have never received this message when flying BA LHR-EU standalone, but for the situation I mentioned, it was on a CX ticket/codeshare, and despite getting my BA LHR-EU boarding pass at HKG, it wouldn't work for entering LHR security until a BA agent at LHR saw my passport (but BA had no problem with me flying the same flight a week before)
So it was the latter scenario you described except that I already had a BP. (Out of interest I tried to reissue my BP at the LHR check-in kiosks after I was rejected by security but before I went to a human, and it wouldn't even let me "log in")