Honoré Fragonard, The Portrait of François-Henri d’Harcourt. Photo: Bonhams.

LONDON - A major work by the 18th century French artist Jean-Honoré Fragonard, The Portrait of François-Henri d'Harcourt, will lead Bonhams sale of works from the renowned collection of the German philanthropist, the late Dr Gustav Rau. The proceeds will be used to benefit UNICEF. The sale will take place at Bonhams New Bond Street on 5 December. 

It will be one of the most important sales in the inaugural season of auctions to be held in Bonhams new saleroom which is being built at a cost of £30m and is due to open in October.

One of Fragonard's famous 15 fantasy portraits, The Portrait of François-Henri d'Harcourt is the most significant of the artist's works to appear on the market for many years. Only two other fantasy portraits remain in private hands making this painting rarer than portraits by Frans Hals, Joshua Reynolds or even Rembrandt. Estimated at in excess of £10million, it has only changed hands once in its 250 year history when Dr Rau acquired the picture from the Harcourt family in 1971.

Bonhams Director of Old Master Painting, Andrew McKenzie, said, "There are always those rare occasions when the work of an artist who is widely regarded as a genius appears on the market. In the world of Old Master Paintings, however, it is almost unique nowadays to sell one of the very masterpieces for which that artist acquired his reputation. Such is Fragonard's Duc d'Harcourt. This is a work of dazzling accomplishment that has been the subject of considerable praise and debate among scholars. As is the case with truly great art, Fragonard here transcends the constraints of his own age to create a tour de force that holds its own today alongside the finest achievements of modern civilisation."

François-Henri d'Harcourt was born in Paris in 1726 into an elite French family and served as a general in the French army, as governor of Normandy and as guardian to the young Louis XVI. He was a member of the French equivalent of the Privy Council and was elected a member of the Académie Française, in 1788. Forced to leave France following the 1789 Revolution, he served as ambassador to the British Court for the exiled Louis XVIII from 1792 and died in Staines in Middlesex in 1802.

Jean-Honoré Fragonard (1732-1806) was a master of genre painting and a leading exponent of the Rococo style of which The Swing in the Wallace Collection in London is probably the best known example. In great demand as a portraitist in the dying days of the Ancien Regime, Fragonard fell on hard times after the French Revolution and although he continued to live in France he died in obscurity and poverty.

Fragonard's fantasy portraits – often depicting friends and acquaintances - were painted quickly with bold, fluid brush work which anticipated the Impressionists in bravura and technique. This style was referred to by some contemporaries as the artist's, 'swordplay of the brush'. The Portrait of François-Henri d'Harcourt is unusual among Fragonard's fantasy portraits because the subject is identified. Many of the other portraits are personifications of the arts rather than representations of named individuals.

Among the other outstanding works in the sale are a 15h century depiction of the Crucifixion by an unknown German artist (£1,000,000– 1,500,000); a portrait of the Duchess of Montebello by Pierre-Paul Prud'hon (£700,000-1,000,000); 'Le grand noyer à l'Hermitage' by Camille Pissarro (£200,000-3000,000); and 'Courtyard with flowers' by Joaquín Sorolla y Bastida (£150,000-200,000).

15h century depiction of the Crucifixion by an unknown German artist (£1,000,000– 1,500,000). Photo: Bonhams.