Windmill Hill, Avebury Trusloe July 2002.
Original formation. Picture by Colin Andrews
Picture below: Shows a day 2 attempt to 'checkerboard' the segments of the original circle. Note that if it had been completed, (very difficult, since the lines are so closely spaced, and it gets increasingly harder to flatten the long extended segments as they move inwards) the checkerboarding would eventually have to flatten the long segment, which itself adjoins a flattened area. White meets white! Big mistake I think, since they had already formed that segment as a 'standing' segment in the original lay. Although the final result may well have been accepted as visually satisfying by many. Zef Damen's reconstruction certainly looks good, if it had been achievable.. Anyway, they gave up, either because it got too fiddly to flatten those long thin segments, or they realised their error, or maybe they were just interrupted.
Even the original formation is not perfect. So only 9 out of 10 for execution. Excellent design though. Picture Steve Alexander.