Signed below the image.
Literature: Not in W. Baron, Sickert. Paintings and Drawings, New Haven and London, 2006, but confirmed by her in Sale Catalogue, The Fine Art Society, Sickert From Life, London, 2013, n. 6, illustrated.
Provenance: London, The Fine Art Society, 2013
Exhibitions: London, The Fine Art Society, Sickert From Life, 2013, n. 6.
The identity of the lady portrayed in this delicate pastel is not known to us. However, the elegant woman resembles Celia Brunel, Lady Noble (1871 - 1962), portrayed by Sickert in 1905 (Bath, Victoria Art Gallery, inv. BATVG : P : 1948.269). 
The artist had met her and her husband William Saxton Noble through his close friend and colleague Jacques Emile Blanche.
Alternatively, the sitter could be either Sickert's first wife Ellen Cobden (c.1848 - 1914) or Canadian painter and Sickert's friend Elizabeth Adela Forbes (née Armstrong, 1859 - 1912).
£ 25,000.-