Ok the OP did make a royal mess of this by not checking his documentation BUT if I have understood this correctly BA flew him OUT of the country on the first leg of this journey on exactly this expired piece of ID to begin with. That would not have been legal either! Now by doing this BA also violated the rules - this can therefore not totally exonerate them now on the return leg. In reality they F***** p as badly as the OP did and should be doing everything to help their passenger since BA illegally brought a passenger to wherever he is now because they missed the expired document on the exit leg.