Sanquhar Castle is difficult to decipher being much altered, allowed to ruin, consolidated, only to fall into ruin again but it seems to date from 1400 with additions from each century until the 17th after which it was abandoned.
The Marquess of Bute, a lover and restorer of buildings of the middle ages, undertook a period of consolidation from 1895-1901 but died before work was completed. His replacement masonry is clearly visible by his use of different material in order not to confuse with the old.
Unfortunately, the castle is once again in a critical state and much tumbled even since the writer has known it. This highlights the fact that simply to consolidate does not guarantee a structure's survival - there must be a plan for long term use