Thanks to James Denham for this photo and information which he has posted on Geograph. New things come to light all the time!
A Covenanters' guard house NT867 532
The lower half of
this old building is said to be a guard house for Covenanting soldiers
and was probably built to protect a nearby Conventicle in 1670. At the
Conventicle at Allanbank, formerly known as East Nisbet, The great
convenanting minister, Reverend John Blackadder, offered communion to an
audience of over 3,200 people all keen to preserve Scotland's chosen
church amidst the onslaught of Royalist soldiers.
As you will notice, the lower half of the building contains gun loops while the top has been added much later to form a shed.