Silbaby 17
Image by jimit

Apologies Nigel and Pete I got one of the digits wrong for original ref but with a 10 fugure it turns out very close to the Silbury -Sanctuary line only 25 m max off . At just over a kilometre away from the Sanctuary that's not bad .

I've just discovered my wifes mobile has gps.
I will try to get accurate measurements from Silbabys center, edge and base as soon as I can.
PeteG