I fly often between London and east coast USA (usually New York or Boston) - and every single time up until now the flight would go along the great circle route.
I flew yesterday from Boston to London - and to my mild surprise the flight path went a lot further south - almost along the parallel. I can't get the full flight radar replay (I guess you need a paid membership for that), but here is a picture I took of the inflight progress display a couple of hours into the flight.
This was flight VS158 (actually renamed to VS1158 due to change of destination airport).
Why would such an unusual path be chosen? I understand that it's unlikely we'd know the exact reasoning for this particular flight, so I'm wondering how and why decisions to route this way are made.
Edited to add: the flight was on 6 August 2019.