Early next month, a fascinating portrait by William Orpen comes up for sale at Phillips of London, which expects to get £20,000 to £30,000 sterling for it.

Part of the interest in this work lies in the extensive documentation of its creation, related in a series of letters from the artist to his young wife Grace. The story is told in Bruce Arnold's biography of Orpen, first published in 1981 and still, after almost 20 years, an invaluable source of information. It was after his success at the winter 1900/1901 exhibition of the New English Art Club that Orpen first received a commission - for which he was paid in advance - to paint the young daughter of Manchester businessman Sam Hughes, who owned the Sherratt and Hughes bookshop. At the same time, he was offered a number of other jobs, including a portrait of the railway entrepreneur James Staats Forbes, whose collection of Barbizon paintings would come to Dublin a few years later and form the basis of the city's municipal art gallery.

As a result of these demands on his time, Orpen only started work on the picture of Clara Hughes in 1902. Bruce Arnold suggests the original commission may have come via the art dealer and collector Hugh Lane, who was a friend of the Hughes family and sometimes stayed with them (Clara Hughes would later remember his piano playing). But this seems unlikely as he only came to know Orpen in 1904, by which time the painting had long been finished. Later Lane would become an important conduit for important commissions, such as the large 1907 portrait of the Vere Foster family which is now in the National Gallery of Ireland.

More likely Sam Hughes was impressed with the work of an exceptionally talented artist then just beginning his career and already making a name for himself as a portraitist. As Arnold points out, during the first decade of the 20th century, Orpen gradually assumed the mantle of England's premier portrait painter which had formerly been held by the American-born John Singer Sargent.

The picture of Clara Hughes posed particular challenges as work featuring small children always does. In old age, she recalled being "very frightened" of the artist and, in turn, he found her a difficult subject. As he wrote to his wife, "If the child could only keep steady, there might be some chance, but she tumbles about till I get angry and then retires crying."

In one letter, he sent Grace Orpen a sketch of how the finished work would look although advising "this is not very like it but it will give you a slight idea". Clara Hughes was distracted as much as possible with books, of which there are several in the portrait, one on her lap and others on the floor around her. "I fear it is a work I shall not be proud of in the future," he worried, but when the picture had been completed and presented to the subject's parents, he informed Grace "It was received here with rapture so at least it pleases somebody."

In fact, ever since the commission, ownership of the painting has passed by descent and this is therefore the first time it has come on to the market. Given its considerable charm and well-publicised history, the portrait ought to excite great interest when offered for sale at Phillips on June 6th.