Arthur, 1st Marquess of Donegall 1739-99 (c.1780). Gainsborough, Thomas 1727-1788. During the eighteenth century full-length portraits were the most admired and expensive commissions as they posed the greatest artistic challenges. Gainsborough was a highly accomplished landscape painter, as well as a portraitist of great skill and sensitivity, and in this full-length portrait he has introduced a delicate, atmospheric landscape that serves to lighten the formal elegance of the sitter?s pose. Arthur, 1st Marquess of Donegall, was a member of the Chichester family, who had played a major role in the early history of Belfast.