There are two basic possibilities. One is that Mingary was a local product, with a local design responding to local requirements, and built by local workmen using local techniques which had developed over a long period. Ross Cameron of Addyman Archaeology, who came all the way down to Kilchoan last week to give us a thought-provoking talk on the dating of West Coast castles, subscribes to this view - and his arguments are very cogent.
I confess I liked Ross' argument, that the castles of the west coast show little affinity for castles elsewhere in Scotland, and certainly no design connections to Norman-English castles; and that the Highland Scots had plenty of previous experience in building large stone structures. I liked Ross' argument until people began to talk about the mortar used at Mingary.
"The mortar is similar to 'Roman Concrete' requiring both the use of hot lime and hydrated lime reacting with a pozzolan - in Mingary's case, whinstone. The mortar's structural integrity is ensured by its rapid curing, making it possible that Mingary was built in two, three or four years. This is significantly less than the timescale I first believed, of circa seven years.
"This building technology is generally believed to have been 'lost' after the fall of the Roman Empire, being rediscovered with the discovery and translation of Vitruvius (around 1414AD). The evidence from Mingary's mortar (around 1300AD) makes it clear that this was not the case. The mortar used in contempory buildings in England does not appear from evidence to use the reactive quality of the two limes in conjunction with the catalyst properties of pozzolan.
"My views are speculative but I believe this construction methodology was either imported into Scotland in the late twelfth or thirteenth century from the Middle East, possibly during the collapse of the Kingdom of Jerusalem between 1265 and 1291, or the only other hypothesis is that construction methods had survived in the Highlands from the time of the Roman occupation."
Francis' ideas suggest that someone who had, perhaps, worked on castles for the crusaders in Palestine, such as Krak des Chevaliers, above, and learned there the use of Roman concrete, later returned to Scotland and was involved in building Mingary. I would love to know whether any other contemporary castles, particularly along the west coast, have the same mortar. If they do, then the idea of an itinerant, ex-crusader master castle builder becomes more likely.
Photo of Castle Tioram courtesy Dave Wilkie on Wikimedia Commons, link here.
Photo of Krak des Chevaliers courtesy Wikipedia, here.
Many thanks to Ross Cameron and Francis Shaw.