London: A ghostly image of Mary, Queen of Scots, has been found under a portrait of a Tudor aristocrat that has been hanging on the wall of a historic house in outer London. Her portrait may have been considered dangerous, left unfinished and then overprinted by the nervous artist, in the political turmoil after she was executed in 1587.

Her blurry image, recovered through an x-ray, will be on display at the Scottish National Portrait Gallery together with the portrait of Sir John Maitland, a courtier who became lord chancellor of Scotland, which has hidden it for almost 450 years. The resurrection of the image of Mary was described as “a fascinating discovery” by Christopher Baker, the director of the gallery.

The lost painting was recovered through a major research project between the National Galleries of Scotland and the Courtauld Institute of Art, which brought together a group of portraits by Adrian Vanson and Adam de Colone, two artists who came from the Netherlands to work in Scotland in the late 16th century.

The concealed portrait was revealed when Caroline Rae, from the Courtauld, X-rayed the painting and saw outlined in the lead-white paint that blocked the rays the shadowy figure of a woman, which, from the outline of her face and dress and the pose of the figure, closely resembled other near-contemporary portraits of Mary.

Despite the fascination with Mary in her lifetime and since, there are few authentic contemporary images, probably because long before her execution she was a controversial figure, embroiled in the religious upheavals of the day, and implicated in her husband’s murder. She was forced to abdicate in 1567, then imprisoned in England by her cousin Elizabeth I, and executed when she was implicated in plots for a rebellion.

The portrait of Maitland is dated 1589, just two years after her execution. It normally hangs in Ham House, a National Trust mansion on the Thames near Richmond in south-west London.

David Taylor, a curator at the National Trust, said: “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 dimension to it. 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.”