There are 4 recognised cairns in this patch, with a couple of other possibles. They've all been robbed out to some extent, but the 10m diameter one at NY79627084 has a clearly visible cist cover in the middle. Close by is another 10m jobby, at NY79617080 and a smaller one of 6m at NY79577086. A bit further towards Kings Crags is the largest of the bunch, at 17m, grid ref. NY79867105.
Whilst there is no direct evidence, it's got to be a fair bet that these cairns were placed in reference to the phenomenal stone of Gwenhyfar's chair at queen's crags, which is easily visible in the pictures, which also played a possible role in the placement of the two small stone circles nearby. It's a darn complex landscape around this part of the world.
[A] local tradition of King Arthur is told by Dr. Bruce: "To the north of Sewingshields, two strata of sandstone crop out to the day; the highest points of each ledge are called the King and Queen's Crag, from the following legend. King Arthur, seated on the furthest rock, was talking with his queen, who, meanwhile, was engaged in arranging her 'back hair.' Some expression of the queen's having offended his majesty, he seized a rock which lay near him, and with an exertion of strength for which the Picts were proverbial, threw it at her, a distance of about a quarter of a mile! The queen with great dexterity caught it upon her comb, and thus warded off the blow; the stone fell between them, where it lies to this very day, with the marks of the comb upon it, to attest the truth of the story. It probably weighs about twenty tons."
One would imagine the comb marks are those clearly seen at the top of the massive stone in Hob's photo.