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That bit where it goes through the cutting and out into the valley is known as Chickenshit Gorge. When I was a child (and lived three miles from there) the cutting was blinding white, having just been cut through the chalk. So white was it that it actually caused accidents on sunny days, and was also quite crumbly. I recall seeing bits of the chalk fall off and into the road. In the 1970s it was sprayed regularly with liquid guano from the local chicken farms, which encouraged the growth of lichen. This holds it all together and gives it the greeny-grey appearance it now has.

This has been your Oxfordshire anecdote of the day.