This whale first surfaced behind us while we were sailing south at around 4 knots.
It then stayed with us for about 45 minutes, occasionally crossing in front of the boat while we tried to guess which side it would surface on next.

About 13-14 meters long, (40-45 ft.), by comparing to the boat length.

At the time, we thought it was a Bryde's whale, based on the ID guides we had on the boat. Now, I don't know, and reading what's on here and wikipedia, it sounds like they might be still sorting out the taxonomy.