It is the only known painting of her as queen and scientific tests indicate that it was painted within her lifetime, or possibly shortly after her death.

It had been relegated to a drawer after being dismissed as an 18th-century copy. However, dendrochronology, or tree ring analysis, has established that the panel on which it was painted was felled in the 16th century and it can be dated between 1560 and 1592.

The portrait had been in the collection of the Earl of Cowley (1866-1919), but nothing is known of its earlier history. It was purchased by the gallery in 1916 at Christie’s, London.

In the 1960s Sir Roy Strong, an expert on the period, catalogued it as a later copy. He did not, however, have the benefit of scientific analysis; nor did he see the painting after conservation work. This has revealed an original oval background with a marbling effect, which had been overpainted with dark brown paint, possibly in the 18th or 19th centuries. The repaint, reasons for which remain a mystery, had obscured Mary’s name round the edge.

On being told of the discovery, Sir Roy said: “I’m delighted. I catalogued it with no technical department. I was looking (at it) through a glass darkly.”

After sparking rebellion among the Scottish nobles with her marital and political actions, Queen Mary was forced to flee to England where she was beheaded in 1587 as a Roman Catholic threat to the English throne. After her execution she would not have been a popular figure to have on display, but, according to Tarnya Cooper, curator of 16th-century paintings at the National Portrait Gallery, she would still have been a curiosity.

The portrait, which measures 250mm by 190mm (about 10in by 7½in) , is in oil and is by an unknown artist. Dr Cooper said that the restoration had revealed an exquisite painting. “The costume is beautifully done, the eyes and face delicately painted.” She believes that it could have been painted for one of Mary’s supporters.

The portrait depicts the red-haired Queen of Scots (1542-87) after her return to Scotland following the death of her husband, King Francis II of France, in 1560. This was a period in which she married Lord Darnley and gave birth to her only child, later James I of England. After Darnley’s mur-der in 1567, Mary was forced to abdicate and escaped to England only to be imprisoned for the remaining years of her life.

While in France as a child and as a young woman, Mary was drawn several times by the court artist François Clouet. But from the turbulent period of her life in Scotland, only images on coins and one miniature appeared to have survived.

She later sat for a portrait miniature by Nicholas Hilliard, whose original is in the Royal Collection. All later images of her are based on that.

In the rediscovered portrait she is wearing a cap that would have been unusual for women. Dr Cooper said: “It’s possibly a man’s. The portrait shows her as an independent character.”

The painting will be displayed in the Tudor Galleries at the National Portrait Gallery, London, from today.

A TURBULENT LIFE

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