Graham Hancock made a big thing about the fact that the Orion alignment of the pyramids would have been much more accurate in the past that it is today, owing to the Earth's precession. This may have been perfectly valid. However, he projected back for the best alignment and came up with a date of 10,500BC, which doesn't match any of the other evidence for the date of construction. He was duly ridiculed by the establishment.

It would be interesting to do the same projection for Thornborough. If the best alignment coincides with the accepted chronology for the construction of the henges, then the case is strengthened considerably.