The portrait, by French artist François Guérin (fl.1751-91), shows the political philosopher seated at a desk with quill pen and envelope. It previously went under the hammer at Bonhams in 2015 when it was catalogued simply as ‘French School’. However, London dealer Nicholas Bagshaw discovered Guérin’s signature during cleaning.
It is now offered with an estimate of £10,000-15,000 at Lyon & Turnbull’s sale The Classic Tradition: European Art from 15th-19th Centuries on October 30. Organised by Rohan McCulloch, the sale is the firm’s inaugural event at 10-11 Carlton House Terrace.
The 2ft 6in x 2ft (76 x 61cm) oil on canvas, probably dating to the 1760s, is one of only a handful of lifetime portraits of Rousseau that are known. It was painted around the time he wrote two of his most famous works, The Social Contract and Emile, or On Education.
It is now offered from a London collection with a provenance back to Jean Francois Xavier Rousseau, the author’s cousin.