This is probably Major John Singleton of the Royal Artillery. According to Hart's Army List (1860): 'Major Singleton served in the Eastern campaign of 1854-55, including the affairs of Bulganac and M'Kenzie's Farm, the battles of Alma, Balaklava and Inkerman, the siege and fall of Sebastopol, and repulse of the sortie on the 26th October 1854 (Medal and Clasps, Knight of the Legion of Honour, and 5th Class of the Medjidie). Served in India in 1858, and commanded the Artillery in the repulse of the mutinous Sepoys at Mooltan on 31st March.'

John Singleton eventually rose to the rank of Major-General in the service of the Royal Artillery.

In 1856 he married Catherine Marianne Barry, daughter of Major-General Philip Barry. He died without issue.

The daybooks, which list the sitter as Major Singleton, show a variant pose in which Singleton is seated astride the chair.