Ferrara said the survival of the painting was most likely to due to “happenstance” as it had been painted on to plasterwork which had been difficult to scrape off during the previous centuries.
Medieval wall paintings can be found around the country, but Ferrara said finding one in Durham Castle, which had experienced so much change over the centuries, was “exceptional”.
The researchers were able to date the artwork by comparing it to other paintings.
Ferrara said the painting was probably commissioned by the Bishop of Durham, though they did not know which one, and they believed it would have likely extended across the entire room.
“You have to imagine going into a huge room and it would have been covered in this really incredible and bright coloured wall decoration,” he said.
“It really underscores that sort of power and status the Bishop of Durham had during the medieval period.”
Ferrara said the room had since been re-panelled with a small cut-out so the wall painting could still be seen.
The university, which owns Durham Castle, was now figuring out whether the painting could be incorporated into public tours of the site, he said.