George John Cavafy was a Turkish merchant and partner in G. J. Cavafy and Co, and an important collector of the paintings of Whistler. At the time of the 1881 census he was living at 2 Upper Berkely Street with his Turkish born wife Mary (aged 65), and their son John Cavafy, who was a physician, with his wife and daughter.
Cavafy made a number of significant purchases from Whistler in the 1860s, as well as aiding other sales of Whistler's work. The Coast of Brittany (YMSM 37) was sold by Whistler through Cavafy to his half-brother G. W. Whistler for £84 in 1863. In 1863 Cavafy bought The Last of Old Westminster (YMSM 39) for 30 guineas following its exhibition at the Royal Academy in London. In 1863 Cavafy also bought Battersea Reach (YMSM 45) for £30. In 1867 he purchased Variations in Flesh Colour and Green: The Balcony (YMSM 56) for 30 guineas. Harmony in Blue and Silver: Trouville (YMSM 64) was given to Cavafy by Whistler at some point before 1878 when he cleaned and restored it, and replaced its frame with a new one designed by himself. Whistler then demanded payment which Cavafy refused. In a letter to Cavafy's son, Whistler suggested that the picture should be returned to the artist, saying 'you have had it quite long enough' (#00549).
John Cavafy frequently acted on behalf of his father in matters of art and business. In 1889 Whistler sought to buy The Last of Old Westminster (YMSM 39) and Variations in Flesh Colour and Green: The Balcony (YMSM 56) back for £180. Cavafy refused. Whistler had borrowed Variations in Flesh Colour and Green: The Balcony (YMSM 56), and John Cavafy, writing on behalf of his father in March 1889, demanded it back (#00552). He later refused to lend Whistler further works (#00555).
The Last of Old Westminster (YMSM 39), Battersea Reach (YMSM 45), Variations in Flesh Colour and Green: The Balcony (YMSM 56) and Harmony in Blue and Silver: Trouville (YMSM 64) were sold to the New York dealer E. G. Kennedy for £650 by Cavafy's son in June 1892.
UK census 1881, from http://www.familysearch.org (accessed 2004); The Times, London, Saturday, 30 May 1891; p. 1; The Times, Wednesday, 6 November 1901, p. 11.