See this -
http://www.youtube.com/watch?v=6IsOPkfWYBI&feature=channel
As predicted, said to be deliberate. Great sequence though. Shame they moved the camera to preserve the effect. Suggests the roll isn't quite parallel - but if they'd shown the sun a little above the slope like the other one does it would have worked without needing to shift position. You can tell that by referencing the position of the tree lined up with the extreme left edge of Silbury which stays the same through most of the sequence.