Greyweather's spot on with this one - a classic chambered cairn.
First thoughts upon looking at the map were...uh oh... forestry... but the track's clear all the way and the cairn stands proud and treeless (well, save the little fella in the picture) above and to the left of it.
The cairn is substantial indeed with a small, intact chamber. I sat inside relaxing out of the sun [strange but true], waiting for someone to arrive and spoil the moment. But no-one did...
The forestry track entrance is somewhat obscure being, as you would expect, un-signposted. Make sure you have the OS map and if you are heading north and pass a fine waterfall on your right, you've gone too far.
First, credit is due to the Forestry Commission. Often criticised in these postings for their close-planting policy, this is an example of how it should be done.
There is some planting to the N but it is kept well clear of the site and 360 degree views have been maintained. Indeed, it looks like the older, pre-forestry trees around the cairn have been felled to open up the site.
The cairn area has then been enclosed in a deer fence with a stile put in for access.
Then there is the site itself.
You come to expect sites to be either cairns with no chambers visible or chambers with little or no cairn material - certainly none above chamber height.
This one has both. A cairn so well preserved that you can still feel under your feet the outline of the horns at one end. And it's not covered in vegetation.
Plus a chamber still well preserved and roofed at its inner end. Accessible enough to shelter from a shower - as I can testify.
Later, sitting having my lunch, I had a thought.
If this were a stone circle in a comparable state of preservation, lots of people would visit it. Because it's a chambered cairn it probably gets very few visitors. Perhaps I should be grateful for that.
Easy access but with a high stile to climb at the end.