Im not sure if I've seen this discussed before, so please merge if it has but on reviewing a recent booking I've just noticed an option on the seat map selection for-
Twin Seats
Seats for two
Enjoy a window or aisle seat, with nothing in between when you choose a twin seat.
You can guarantee that you'll only sit beside your travel companion with the seat pairs located at the
rear of our longhaul aircraft (bolding mine).
Edit- Ahh, just noticed the 'Back of the aircraft bit' They're obviously just going to start chargig a premium fee for the seat pairs at the back.
Whilst it was on the Seat Map Key, no 'Twin' seats were available in the old style 777 Y cabin in which I have a seat.