Díaz Padrón argued that the painting was "believed to be, and documented as, a Velázquez original in the 17th and 18th centuries … by the professors of the Royal Academy, including Francisco de Goya". It was only in the 19th and 20th centuries that the painting's provenance was changed, he said, with historians coming to believe it to be a later copy by Juan Bautista Martínez del Mazo, Velázquez's son-in-law and successor as painter to the royal court.

He argued that this was a mistake and that the painting was the first "boceto or modeletto" — a first draft or sketch – painted by Velázquez, which the king then asked him to reproduce on a larger scale, which now hangs in the Prado.

Díaz Padrón said: "Today, the moment has arrived to revise these judgments, and restore the painting's authorship to Velázquez." He said: "I don't see any differences between the boceto and the definitive work … the colours are typical of Velázquez in both pictures."

The debate is anything but settled, however, and the Prado museum denies that the painting in Kingston Lacy, bought by the English landowner and art collector William Bankes in the early 19th century, is an original.

Díaz Padrón says that Lay Kingston painting, is a preliminary study of Las Meninas, but this is unlikely. In the X-ray test performed to Las Meninas, will appreciate, numerous changes, introduced during the process of composition. These changes are only in the original canvas and not in the copy. This is a copy of the basic composition of the canvas of the Prado, once finished. If this was a modeletto, would reflect occult version of the Prado painting, not the final version.

Diaz Padron insists on ignoring the evidence, physical and chemical. According to him: "An artist is not a pigment, not a glue, not a color" but a painting, it is.

Confusion over the works of Velasquez and del Mazo has been around for centuries. 

Aside from the Kingston Lacy painting, the National Gallery paid £10,000 in 1890 for what it thought was a famous original portrait by Velasquez of Admiral Pareja.  For some years now that work has been “downgraded” and is generally thought to be by del Mazo.

What’s always intrigued me is that the Gallery has a fully authenticated del Mazo which, while it bears some similarities to the Admiral Pareja portrait, is much less impressive.  If the Admiral Pareja portrait is a copy by del Mazo, he clearly had some facility in imitating Velasquez’s technique – see also the rather splendid work in York.