The highly visible banner was created overnight on Friday as the referendum headed into the busiest weekend of campaigning.
It was organised by a group called ‘Independence Climber’ who claimed on facebook it had been created by a young woman in need of a lung transplant who had to climb with an oxygen tank.
They said of the event: “No damage to the castle or surrounding area. Nighttime ascent and a successful one. No doubt it will be removed but for now the reflective YES shines bright!”