Hayes writes of the present drawing and that of her mother, the Duchess of Bedford 'As pastels they are exceptional: Gainsborough is not known to have done many... and amongst these, the portrait of Caroline is unique in being half-length rather than the more normal head and shoulders in a feigned oval... This is one of Gainsborough's gentlest and most touching portraits' (Hayes, op. cit., 1968, pp. 222-3). The directness and immediacy of the medium of pastel and the particularly good state of preservation makes possible a unique sense of engagement with the sitter. Gainsborough was able to capture an informal atmosphere most effectively in his drawings and this intimate mood is in keeping with the fact that these pastels were not executed as formal commissions but as personal gifts to the sitters.
Hayes notes that the Duchess's hair, piled up high, was fashionable around the late 1760s, though he notes that she looks younger and more demure than in Gainsborough's portrait of her at Woburn painted in the later 1760s. In the present portrait Gainsborough has combined a broad, bold technique for the textures of the drapery, and a delicate, careful, handling of the chalks for the sitter's face to enable him to capture her serene expression.
Despite Gainsborough's extensive use of chalk in his landscape drawings his pastel portraits are rare. Jeffares, op. cit., lists seventeen identified sitters and suggests that this relatively small number is possibly on account of the fact that he did not fix his portrait drawings. In a letter of 1771 to Edward Stratford he apologises 'I'm sorry your Chalk Drawings got Rubbed as they were muzzy enough at first, as indeed all Chalk Drawings of Portraits must be so small and the chalk so soft'. However it also seems likely that Gainsborough executed so few of these works because they were drawn as favors for the sitters. Of the extant pastels most were executed when Gainsborough was in Bath and the majority are oval in format.
Gainsborough first came into professional contact with the sitter's father, the Duke of Bedford, in 1755, when he was commissioned to produce two landscapes, probably for Woburn. In 1759 he established himself in Bath and renewed his acquaintance with the Bedford family, moving to a house on the Circus only three doors away. On 7 January 1765 Gainsborough wrote from Bath to the Duke's agent 'I should be most obliged if you would acquaint the Duchess that tho' my ill health forbids my following business in London (to which I have frequent invitations) Her Grace may never the less command me at any time to paint any of The Family there'. It seems likely that the present portrait and the one of Gertrude, Duchess of Bedford (Hayes, op. cit., no. 44) were executed during this period. Among the oil portraits that he painted for the Bedfords at this time are bust-length portraits of the Duke and his wife, their daughter Caroline, Duchess of Marlborough (Woburn Abbey), the two nieces of the Duchess of Bedford: Mary Wrottesley and Elizabeth Duchess of Grafton (Woburn Abbey), and two formal portraits of the Duke (destined for the University of Dublin and Woburn respectively).
Lady Caroline Russell (1743-1811) was the only daughter of the 4th Duke of Bedford and his second wife, Gertrude Leveson-Gower. On 23 August 1762 she married her cousin George Spencer, 4th Duke of Marlborough. They had three sons and five daughters and were described by Horace Walpole, who entertained them at Strawberry Hill in June 1784, as inseparable.