Art collector George Lester Winward acquired this beautiful Madonna and child, now known as the De Brécy Tondo, in 1981 at a country-house sale in England. The more he studied it, the more he became convinced that it was painted by the Renaissance artist Raphael — not least because of its striking resemblance to Raphael's sixteenth-century Sistine Madonna in the Gemäldegalerie Alte Meister in Dresden. The art gallery, however, judged it to be a much later copy.

Spectroscopic laser techniques suggest that the De Brécy Tondo is a Renaissance painting. Credit: DEBRÉCY TRUST

So Winward's foundation, the De Brécy Trust, sponsored a series of projects to generate evidence for his claim. It closed, not entirely conclusively, this week, with the publication of a laser Raman spectroscopic analysis of three tiny samples taken from the painting.

The analysis is consistent with the De Brécy Tondo being a Renaissance painting. For instance, one sample was shown to contain massicot, a popular yellow Renaissance pigment that was not used after 1700. By ruling out the presence of some alternative chemicals, the analysis also indirectly suggests a starch-based binding medium, commonly used in Renaissance paintings, and the use of the medieval dye turnsole for the blue robes. The presence of eighteenth-century Prussian blue pigment in discrete patches could be explained by recent touching up, says Howell Edwards, the University of Bradford chemist who did the analysis.

The trust hopes that these data, together with its convincing provenance research, will help persuade art historians, who rely to a large extent on visual assessment when authenticating paintings, that the work is indeed a Raphael, and thus worth millions.