This little 'room' is one I got to the top of last year. The presence of the lintel stones spanning the two side walls above the blocked doorway suggested it was going to be of some depth – and so it proved to be.
The upper fill, as is so often the case at Swandro, was mostly later midden material (inclusive of quite a few fragments of pottery) thrown in over rubble collapsed from the one-time roof. The back wall is slightly corbelled (i.e. angled inwards, achieved by slightly overlapping the stones with each subsequent course).
Below the midden was a thick layer of shillet – the material that is left when the large stones are robbed out all that remains are the small flakes of stone, the dampness of which indicated that there was a fairly solid layer of material not far below.
It was clear by now that the 'blocking' was a bit of a hasty 'Friday afternoon job'; the 'door' was probably in the form of the large oval slab slumped in the passage outside, the top of the side walls were not very stable (the side constructed against the monumental feature on one side comprising a large orthostat with a hollow space behind it) and the other side largely comprising a central pier wall with a large and deep cupboard to one side.
It also became clear that my legs were not long enough to get down into the room from the sides, so the lintel finally came out and access was gained across the blocking wall.
Finally got to the floor level, the stones of which had all been in place before the walls went up. It does not look that impressive because it had been laid over vacuous rubble.
Having finally removed the blocking, I got to walk - albeit sideways around the 'door' - through the entrance, a first for several millennia! But with a door stone like that, I suspect they did not have to access the room very often!