The flight was Virgin V020 from SFO, leaving at 4.30pm US time and arriving at LHR some 9 hours and 40 minutes later. I saw the sun setting somewhere over the far north of Canada and on over Greenland, so the Imap on board was telling me. It also showed that we were just outside of the 'dark side' of the earth (to its north).
Seeing the sun setting on the left hand side of the aircraft was quite confusing till i realised that flying West to East at such high altitudes and latitudes, i could see what was in fact the sun that was shining on the other side of the world, over the north pole, was quite a revelation!...

Thanks for those that confirmed what i saw. Is this possible on other routes, in the southern hemisphere i wonder?