I don't know if I was any more or less convinced of Brennans theory but in this case at least the facts do fit the theory which is a good start!

I was hoping to see the sun rise above Cairn T which was the main reason I was up at 4.30am on a perfectly clear morning to drive from Wicklow, only to find all the hilltops obscured by fog. It was so thick that when the sun began to burn through it felt like the chamber was actually in flight! Looking out the passage all I could see was cloud below and blue sky above because the ground falls fairly steeply in front of the entrance. You can get a sense of it from the pics.