Originally Posted by FrancisA

I think you may be missing the point. TCP is a manual process and can be applied to any booking irrespective of status. In that context TCP (To Complete Party or Total Complete Party, whichever version you like) is a note in the two bookings indicating that they are linked. However, the Gold benefit is that that link is made and the Gold member can request a seat assignment for the non-Gold companion on a separate PNR. (If it was the same PNR, there would be no need for this.) The process is to phone and ask an agent to link the bookings (via TCP) and request (by a message to BA's back office seating department) that the non-Gold passenger is moved to the seat requested (which doesn't have to be next to the gold card holder according to other posts).

What does not happen is that the bookings are merged or that the Gold member gains access to the other party's booking. Also, even prior to the GDPR changes, BA would often ask for confirmation from the other party that they were permitted to amend their ticket for seat selection in the way request. (Being nominated to manage the other party's booking was the easiest way around this). The seating request can take a number of days and is only visible by looking at the non-gold booking to see the newly selected/change seat. Note that equipment changes can throw this out and require a further TCP request - whilst there is a note linking the bookings, the software allocating new seats is unaware of it.