Mary Queen of Scots by an unknown artist, again at the NPG and for the moment at the Holburne. 'This portrait of Mary, Queen of Scots has recently been rediscovered as an image painted within her lifetime or very shortly after her death. The painting had long been considered to date from the eighteenth century, but recent tree ring analysis (known as dendrochronology) has established that the panel was felled in the sixteenth century. The work can now be dated to 1560-92. Recent conservation work has also revealed an original oval background with a marbling effect, which had previously been overpainted with dark brown paint' (here).