A multi-discipline project from Cambridge University has uncovered the hidden secret of Francis I of Brittany – who took an illuminated manuscript made for his first wife, and had it altered to suit his second.

The Hours of Isabella Stuart was originally made for Yolande of Anjou, who died in 1440.

However two years later, with his marriage to Isabella, daughter of James I looming, he painted over his first wife and added an image of St Catherine using cheaper pigments.

Then, when he was later made a duke, the portrait was repainted yet again, to give Isabella a coronet.

The revelation comes from the university’s Miniare (Manuscript Illumination: Non-Invasive Analysis, Research and Expertise) team, which comprises experts in art, humanities, science and technology.

The project is led by Dr Stella Panayotova, keeper of manuscripts and printed books at the Fitzwilliam Museum and Professor Stephen Elliott of the department of chemistry, who are working with colleagues from across the university and around the world.

“Working in a truly cross-disciplinary way can benefit art history, scientific research and visual culture in general, while pushing technology forward at the same time,” said Dr Panayotova.

“Thanks to the imaging techniques we’ve been using, we can see things in these manuscripts that we couldn’t see before.”

Many of the manuscripts they have examined are too delicate to take samples, so they have had to turn to new, non-invasive techniques.

Professor Elliott said: “Part of our research is in the area of medical diagnostics and environmental sensing, where we analyse materials in very thin layers, which is not so different from analysing a painting.

“So we could certainly see what the problems were.”