The fence is unmarked currently, (February 2016), on OS maps. It's clearly intended to exclude deer from what must be a sizeable acreage, (hectare-age?), of ground on the far side, a good deal of which is an 'island' of non-access land surrounded by access land.
Uploaded to Geograph by Trevor Littlewood on 12 February 2016
Photo © Trevor Littlewood, 12 February 2016. Licensed for reuse under this Creative Commons licence