Flying home alone on a long haul flight last night I was allocated a 'B' seat. I sat down and shortly afterwards a couple appeared and sat down in the A and C seats. It was obvious they were together, so I straight away offered to swap seats so they could sit together. They declined, saying "no we always do this'. They then spent the rest of the flight talking across me. I felt most uncomfortable and it was very difficult to relax, sitting in the middle of a conversation. Really unpleasant. I know that some people prefer window seats and some prefer aisle seats, but surely it's unreasonable to force a stranger to be piggy in the middle like that?