Okay, here's my theory.

Originally, the plan was to cover the south face of the Cursus' north bank with quartz, bright white chalk and shiny flint. A row of huge fires would be built in the Cursus at night, creating an Neolithic Son et Lumiere for the megalithic monument they were planning to build on Stonehenge's site.

But, the shaman's protested, claiming the heat of the fires would drive off the rain and clouds, thus allowing the proto-British people to actually SEE the stars for the first time. The shamans feared this awesome sight would convince their followers to become scientific astronomers, instead of shaman worshippers.

The Shaman Heritage Association nixed the Illumination plan after the first two fire pits had been tested, on the trumped-up grounds the fires would cause light pollution and frighten off the night-calling woodcocks.

Ah, what might have been?