The back wall of the barn was leaning out. In fact in the middle of the wall it protruded out beyond the eves of the corrugated iron roof so water running down the roof landed on top of the wall and percolated into the spaces between the stones damaging and washing away the lime mortar.
Inside the loft space of the barn the two big wooden A frames could both be seen to have widened so that their horizontal members had dropped. In one case the horizontal was actually lying on the loft floor
Without being tied in by the horizontal the diagonal members of the A frames are liable to both bend and hinge outwards putting an outward pressure on the top of the walls pushing them or in this case one of them outwards.