>>>The back of the entrance stone is not carved as you had thought, though interestingly enough O'Kelly's report did say there seemed to be a mark on the back of the entrance stone just opposite the doorway, when they placed the door stone into the closed position and leaned it back to the entrance stone it rested in this groove. <<<

That's fascinating, thanks so much, I'll definitely look out for that at my next visit.

>>>They also found worn scratches on the top of the first passage roof stone in front of the roof box, one quartz slab was found which covered roughly half the roof box opening and a missing stone presumably closed the roof box on the other side as it too had scratches where a stone had been pushed and pulled back repeatedly to open and close the roof box. <<<

Oooh err, that's intriguing, especially with it being a quartz slab. I was in Maeshowe last week and the doorstone there is short, to leave a letterbox slit permanently there when it was shut, as are several other doorstones I've read about. Maybe Newgrange is the only place that could be made completely dark inside.

>>>Obviously the 'tomb' was used repeatedly, whether to make observations of the solstice or to warm the cockles of the dead is the question! (Or fertilise the 'womb' of the earth, the explanation of choice of the guide we had last time, you pays your money and takes your theory...)<<<

It's probably a combination of all of those and more, I've a hunch someone will soon come up with some significant lunar 'special effects' there, too.