It looks like I've driven off from the Burbage South car park (the little one at the end of the green drive, not the Fox House) this evening with my guidebook on the roof of the car.
It's in a black nylon Rab cover. It was about 5:30 and we were the last to leave
so I imagine it'll be plainly visible in daylight.
If anyone picks it up I'd be very grateful for its return.