KEY POINTS:
The Mona Lisa is the most famous painting of an enigmatic, beautiful woman - but it has challengers. One is a portrait by Parmigianino of an unknown woman in the Capodimonte Museum in Naples, and there is another here in Glasgow.
The compelling painting of a large-eyed woman is part of the splendid collection of Spanish painting at Pollok House.
The painting has always been attributed to the great Spanish painter El Greco and was at first thought to be a portrait of his daughter and then of his wife. It is certainly an intimate portrait. There seems to be love on both sides of the easel.
The painting is universally known as The Lady in the Ermine Wrap. This is the first oddity - the furs are lynx. She is set against the deepest dark. Her right hand fingers the edge of the fur and her large dark eyes are turned tenderly towards the artist. Her name remains a mystery.
There are other enigmatic matters. El Greco was not Spanish but Greek. He was born in Crete and trained as a painter of icons. His real name was Domenikos Theotokopoulous.
Eventually he went to Venice, which was at the peak of its influence. There, El Greco admired the work of the famous Titian and, for a while, acted as apprentice to his great successor, Tintoretto, and completely absorbed the Venetian manner.
Then he went to Rome where the fame of Michelangelo was at its height. El Greco did not like Michelangelo's style. He thought it was not painterly. His next move was to Spain. He eventually settled in the grand city of Toledo, perched high on its rocky outcrop.
Under the influence of Spanish spirituality, his deeply religious convictions and his ideas about how paint should be handled, he developed a highly individual style with flame-like brush-strokes and long, narrow, distorted faces and figures.
His style was successful in his time but in subsequent centuries it led to his being dismissed as an oddity. Only in the 20th century was it seen as a powerful expressionist manner.
The difficulty with the painting is the face, in particular, is done in a smooth manner different from El Greco's mature style.
It might well be El Greco's wife, except he did not have a wife. He had a constant companion, who, astonishingly for when painters were not rated highly in society, was a noblewoman, Jeronima de las Cuevas. There is no record of their ever being married. They had a son who helped his father and ultimately took over his studio. An inventory of the property of the son, Jorge Manuel, records a portrait of his father but there is no mention of one of his mother.
El Greco was sometimes at odds with the Inquisition, the Church institution that ruled over every aspect of Spanish society. Details of his paintings were challenged. It is astonishing the painter lived in an irregular union without being censured by the Inquisition.
The painting is unforgettable. The face is framed in a hood which emphasises the lovely oval shape of her features. The glance of the dark eyes is challenging and exotic. The fabric of her dress is rich and beautifully painted. The hand that emerges to hold her furs together is delicate, long-fingered and aristocratic.
Lots of scholarly speculation has led to the possibility that she might be the Infanta Catalina Micaela, the second daughter of King Phillip II of Spain and Duchess of Savoy. This has led to controversy over the authorship of the painting.
Because of the style, scholars agree it must have been painted just after El Greco arrived in Spain in 1577 but at that time the Infanta was only 10. The fashion that the sitter is wearing, the lace cuffs and the hairstyle, were fashionable late in the 1590s when El Greco was painting in a very different style.
Some writers suggest the painting was done by the fine female painter Sofonisba Anguissola who was at the court of Phillip II. In some books on women painters, the attribution is confidently asserted, and in an exhibition in Vienna in 1995 it was labelled as by Anguissola.
There is some similarity to a portrait by Anguissola in the Prado in Madrid. Others put it in El Greco's Italian period, and there is even a theory it was painted by Tintoretto. Other painters, including the Spaniard Sanchez Coello, have been advanced as possibilities.
The likelihood is that the tradition is correct and it is by El Greco. His small, intimate paintings were sometimes more smooth than his large works in his mature manner for churches where the paintings needed big carrying power.
The quality is too good for a lesser painter and it is unlikely royalty would have been shown in ordinary clothes and not court dress. The extraordinary intimacy of the glance suggests a close relationship, and it is this intimacy, as well as the remarkable beauty of the sitter, that creates the power of this enigmatic work.
Pollok House is a splendid example of a great house preserved with everything still in place, from the art collection to the kitchen. Sir John Stirling Maxwell, whose family house it was, acquired his outstanding collection of Spanish paintings in the 19th century when painters like El Greco and Goya had almost been forgotten.