andrewmb: As mentioned in pieces_of_8's log the ditches round the field have been dug - or rather excavated. This means that instead of a shallow grassy hollow in front of the beech tree there is a four foot deep gulley.
The place that the cache was hidden is still present in the base of the tree, but the cache isn't there. To get to the cache location now requires climbing into the ditch which isn't very convenient. In addition since it seems to have been deliberately removed rather than accidently caught up in the ditch digging I will archive the cache rather than replace it.