Originally Posted by jplondon
I should be able to now select a seat for my travel companion, right?
No, not right. You should now ask BA to put in a request to Seating Control for a seat next to you - that is the crucial step, the TCP alone is useless (and for non-Emeralds Seating Control will ignore the request)
This process does not give the ineligble pax proper seat assignment rights on MMB.
BTW at least in CW, a seat behind also seems to work (I had 4A, another person had 4B, I requested 3A for a Blue and it was done and assigned).