John Cairns was also a military engineer, and was responsible for designing the impressive King David's Tower at Edinburgh Castle, which was destroyed in 1573.

[2] The fact that round towers are common in Ireland has led to speculation of Irish influence at Orchardton, however no specific link has been found.

John Cairns' grandson William was present, in support of his relatives Agnew and Lochinvar, at the murder of Thomas McLellan of Bombie, outside St. Giles' Cathedral, Edinburgh in 1527.

[3] The part of Orchardton including the castle was sold in 1616 to Robert Maxwell, who had earlier bought the other portions of the estate.

Robert returned to France for a time, before deciding to declare himself a Protestant in order to claim his rightful inheritance.

In 1753 he resigned his commission and returned to Scotland to begin a long lawsuit, which ended in 1771 when he was confirmed as Sir Robert Maxwell, 7th Bt.

The round tower was located at the north east corner of a fortified yard or barmkin, which would have sheltered livestock and provided cellars, a bakehouse, and probably a hall built on an upper level.

The tower itself was reserved for living quarters, and was accessed via a stair, possibly moveable, from the barmkin up to a first floor doorway.