The sitter, née Furnese, firstly married Lewis Watson, 2nd Earl of Rockingham (c.1717-1745), and secondly Francis, 7th Lord North and 3rd Lord Guilford, later 1st Earl of Guilford, in 1751 as his third wife. Francis' first wife, Lady Lucy Montagu, died in 1743 (see lot 56) and his second wife Elizabeth, Viscountess Lewisham, died in 1745 (see lot 59).
Katherine was also painted full-length, by John Baptiste van Loo in 1738 and as Diana, attributed to George Knapton (both paintings are at Rockingham Castle). In 1740 she was painted full-length by Alan Ramsay (The City Art Gallery, Bristol).
Vanderbank trained in Kneller's academy in Great Queen Street and was one of the co-founders of the St Martin's Lane academy in 1720, later attended by Hogarth, Highmore and Seymour. Inspired by the work of Rubens and van Dyck, Vanderbank became an accomplished portrait artist. Among his most successful portraits is a full-length of Queen Caroline, painted in 1736 (Goodwood House, Chichester, Sussex).