The work involved twenty-one sittings for the captain, and eight for the horse, an unusually high number. They took place between February and April 1782, and made Reynolds the sum of £205 (the frame cost an extra ten guineas). The portrait stayed in the family until it was purchased in 1884 by William K. Vanderbilt, who in 1920 bequeathed it to New York's Metropolitan Museum of Art, where it remains today. Not surprisingly considering the number of sittings, Joshua Reynolds paid great attention to this complex composition, and indeed, it must have needed that, with the surface being finished with confidence and panache. The artist's preferred method of applying paint in long smooth strokes is apparent here, with light falling on the figure and on the horse's face. Details are confined to just those that are necessary, so the background is not overcrowded.

It's said that the author Ernest Hemingway proclaimed this a fine painting, and observed that the subject's arrogance came across in the way he stood casually against the tree. Certainly, the captain is very relaxed and sure of himself, with the artist confidently conveying the young man's awareness of his privileged position in society. Sir Joshua Reynolds studied under Joshua Wright of Derby and Thomas Hudson. He revered Old Masters such as Rembrandt, Van Dyck and Rubens, who increased his interest in light and colour, and the use of classical poses, while travels in Italy awakened him to the effects of chiaroscuro.

In 1768 he was appointed as the first president of the Royal Academy, from where he gave his acclaimed lectures "Discourses on Art". His influence went beyond what he imparted to his students, and continued to be relevant to later generations of portraitists, such as Henry Raeburn and Thomas Lawrence. Reynolds took in and reflected the taste and morals of his day, with this portrait of Captain George KH Coussmaker being a typical example. However, he was always interested in new developments in art during the Age of Enlightenment, one of the reasons that he is remembered today.