Sketch of Mary Queen of Scots discovered

An unfinished portrait of Mary, Queen of Scots has been discovered beneath a 16th-century painting.

Experts believe the picture of the woman bears "compelling similarities" to the queen, the Daily Mail reported. An x-ray of a portrait of Sir John Maitland, the Lord Chancellor of Scotland between 1586 and 1595 led to the find.

Conservator Dr Caroline Rae, part of the research team by the National Galleries of Scotland (NGS) and the Courtauld Institute of Art in London was examining the 1589 painting by Dutch portrait artist Adrian Vanson along with his other works.

"Using technical art history, it is possible to illuminate artists' materials and techniques for the first time in centuries, to discern copies and forgeries and to explore questions of authorship and workshop practice," Dr Rae told the Daily Mail.

The sketch was probably abandoned or covered, researchers speculate due to her execution in 1587.

"Vanson's portrait of Sir John Maitland is an important picture in the National Trust collection, and the remarkable discovery of the unfinished portrait of Mary, Queen of Scots adds an exciting hidden dimension to it," David Taylor, curator of pictures and sculpture at the National Trust told the Daily Mail. Adding, "It shows that portraits of the queen were being copied and presumably displayed in Scotland around the time of her execution, a highly contentious and potentially dangerous thing to be seen doing."