I have returned, and this time I shall dispense with any formalities and jump the gate (the stone is indeed more or less on a marked footpath). Rewards: A stone that’s nearly as tall as me and quartz all down one side, a tractor whirred in the background and an unfamiliar bird call. Nothing about but me and the stone,(and a bug named tony) just the way it should be.
Blimey, another Mid-Wales one to visit. Glad you persevered Postie, definitely worth the return. Pesky farmers, eh? At least he didn't try to get you to marry his daughter or anything like that.