Originally Posted by
chriswiles
He can only check through the First Wing if Gold or travelling First (as he's not part of your booking, so completely separate). When you then go First security, you end up directly in the First lounge.
This has mostly been covered elsewhere, but for the avoidance of doubt, this is only true if the partner arrives unaccompanied. Should both be together, anyone travelling in First, or as a OneWorld Emerald, is entitled to one guest travelling on a BA-operated flight (with some nuance around theoretical non-BA operated flights out of T5 - I don't think there are any at the moment, certainly not in this particular case).