The monument at centisquare 83 (not yet photographed for Geograph) was erected by George Gordon, 4th Earl of Aberdeen, to the memory of his brother Sir Alexander Gordon, Colonel Scots Guards, and ADC to the Duke of Wellington. Sir Alexander Gordon was killed at the Battle of Waterloo on 18th June 1815.
The Duke wrote of him ‘He had served me most zealously and usefully for many years, and on many trying occasions; but he had never rendered himself more useful and had never distinguished himself more than in our late actions. He received the wound which occasioned his death when rallying one of the Brunswick battalions which was shaking a little; and he lived long enough to be informed by myself of the glorious result of our actions, to which he had so much contributed by his active and zealous assistance.’
See also a review of Sir Alexander's published letters of the period
http://www.napoleon-series.org/reviews/memoirs/c_gordon.html