So I had an interesting experience last night due to the cancellations disruption....not related to getting re booked or hotel ( luckily my Corp TA sorted that for me) but I could not exit the airport. BA staff at T5 directed passengers to exit via gate 19. This led us down to the main arrivals area, mixed with all other international arrivals. There were around 100 domestic passengers with no passport ( including me) who could not exit. Border Control would not let us through until they manually verified everyone ( not sure what this involved...phone calls to Home Office staff?). They said that BA should not have sent domestic pax this route to exit ? Should there have been another exit for Domestics?
Anyway, lesson learned. Carry passport for Dom flights from now on!!