45m, 2 pitches. This route is described in Northern Highlands North as 'Original Route' - the vague grooves up the face just left of the arete.
Photos (online) of the 1970 FA of North Gaulton Castle show that team went directly up the south side of the east arete, thus the more accessible (and popular) corner cracks just to the left are added here under their 1979 name, Out of the Deep.
Follows the prominent crack line on the right side of the south face. From sea level (low tide) at the bottom of the landward arete the first 15 feet of climbing to a good ledge can be problematic. This short hard section is unprotectable and has a technical grade of 5b. There is however a crack line starting under the roof, 20 foot to the left of this arete. If this crack is dry it can be led at HVS with a big move on to the ledge (The bolt here gone in 2016). From this ledge climb up obvious cracks and horizontal breaks to a large ledge/platform on the landward arete, about a third of the way up the stack. The second pitch follows the big crack through an open book corner to the left of this belay ledge on the south face. At the top of the open book corner walk left on a huge ledge to the bottom of a well defined further open book corner/groove in the center of this huge ledge, climb this to the summit. On the last few meters the rock becomes looser.