It's a stone shelter build by a vicar in 1846 for travellers across the fell.
Worth going just for that. The limestone on top is excellent as well.

https://www.visitcumbria.com/sl/hampsfell-hospice/

It looked quite something as we approached through the mist.

Odd that it's marked as a pillar on the OS 1:25000. No trig there just a bolt.