The Vanishing Velazquez by Laura Cumming.

If only there was a photograph of Snare's portrait, we could see whether it carried something of Velazquez, or nothing at all.  It would allow us to see what he saw, what he revered, above all what he truly loved -- I believe in his sincerity -- in this work of art that wrecked his life.

If the art of Velazquez teaches us anything at all it is the depth and complexity of our fellow human beings.

-- Laura Cumming, The Vanishing Velazquez (Scribner,2016)

In 1845 bookseller John Snare of Reading,England bought a portrait at a liquidation auction that he was convinced, after he cleaned it, was a portrait of Charles I by the Spanish painter Diego Velasquez.  Snare paid eight pounds for the painting and spent the rest of his life proving that it was indeed a Velazquez and showing it everywhere from England to America. 

The painting was last seen when Snare tried to sell it in America in 1898; no one knows now if it still exists or, if it does, where it is; there is no surviving photograph or any other picture of the painting.  Those of us who have been to the Prado and seen Velazquez's paintings -- especially the exquisite Las Meninas,c.1656 -- can understand how a painting of Velazquez's can ensnare (pun intended) one, if Snare's painting was indeed a Velazquez. 

Cumming's book is a slightly uneasy mixture of detective story -- as she follows in Snare's footsteps in his attempts to authenticate the painting and uses the resources of the internet to try to trace it -- and art historical connoisseurship, as she captures much of the appeal of Velazquez's paintings. Whether of not one agrees with her interpretations I urge one to travel to Madrid to see Las Meninas or at least to the Metropolitan Museum to see the extraordinary portrait of Juan de Pareja, c. 1650