Cable size... conflicting results

[JohnW2]

The stone wall is described as limestone rubble and lime mortar and can be thermally very conductive when moist and good insulation when dry,

FWIW, dry (which is obviously what matters) limestone seems to have a thermal resistivity of around 0.8 K.m/W, well under the 2 K.m/W maximum value for Installation Method B - so, with a grouping de-rating factor of 0.8, your cable ought to have a CCC of around 41.6A (using Table 4D2A, since Table 4D5 doesn't include Method B)

Kind Regards, John.